System and method for inserting advertisement content in 360° immersive video

ABSTRACT

A system and method for inserting secondary content, e.g., advertisement content, graphics, images, etc., in a 360-degree immersive video environment. When a request is received from a client device for playing a video asset, a plurality of video tiles of the video asset are selected to be assembled as a video frame for delivery to the client device. A portion of the video tiles are identified that can be replaced with a corresponding set of advertisement content tiles, e.g., based on gaze vector information and/or a tile metadata specification containing advertisement insertion availability timing information with respect to each of the tiles of the video frame. After replacing the portion of the identified video tiles, the corresponding set of advertisement content tiles and remaining video tiles are assembled into the video frame including the advertisement content tiles at select locations, which is transmitted to the client device.

TECHNICAL FIELD

The present disclosure generally relates to communication networks. Moreparticularly, and not by way of any limitation, the present disclosureis directed to a system and method for inserting advertisement contentin 360° immersive video streaming.

BACKGROUND

The introduction of virtual reality has brought new applications to theforefront in addition to improving several existing technologies. Oneimprovement over existing technologies can be seen in the case of 360°immersive video, also variously referred to as panoramic video,360-degree video or 360 video, and the like.

360-degree video offers the user with an immersive “being there”experience. The increased immersion of virtual reality can easily beapplied to video, providing superior user experience over thetraditional video that is projected on flat surfaces. The popularity ofnavigable 360-degree video systems has also grown with the advent ofomnidirectional capturing systems and interactive displaying systems,such as head-mounted displays (HMDs) or headsets. However, contentproviders have been contending with bandwidth constrained networkenvironments to deliver 360-degree video content in an efficient way inorder to ensure a satisfactory viewing experience because 360-degreevideo assets are ultra high resolution spherical videos, which containan omnidirectional view of the scenes requiring enormous amounts ofdata.

Current 360 video headsets are 2K-resolution display devices, covering1K per eye. In order to achieve the best quality in the headset, atypical network requires sending an 8K 360 video stream to the device.It is known that video compression allows efficient utilization ofbandwidth in a media streaming network by reducing the number of bits torepresent a picture. Whereas advances in video compression technologiescontinue to grow apace, several lacunae remain in the field of 360 videodelivery and display with respect to efficiently managing bandwidth intoday's network architectures, including the ability to provideadvertisement content in a 360-degree video playback environment,thereby requiring further innovation as will be set forth hereinbelow.

SUMMARY

The present patent disclosure is broadly directed to systems, methods,apparatuses, devices, and associated non-transitory computer-readablemedia and network architecture for effectuating optimized 360° immersivevideo viewing experiences including, inter alia, the ability to insertvarious types of secondary content, e.g., advertisement content,graphics, images, etc., in an immersive video playout session. In oneaspect, certain embodiments are directed to optimized encoding schemesthat may be implemented in an arrangement involving encoding of sourcevideo streams into tile-encoded streams having different qualities. In afurther aspect, certain embodiments are directed to utilizing user gazevector information in determining tile weights based on the location oftiles with respect to a user's viewport. In still further aspects,example embodiments are directed to tile selection and bandwidthannealing schemes where bandwidth-optimized tiles are selectedresponsive to gaze vector information and/or tile availability metadataspecification that may be stitched along with tiles for advertisementcontent into a multiplexed coded video sequence for providing anenhanced viewing experience while continuing to receive advertisements.

In one example embodiment, a method for inserting advertisement contentin a 360-degree immersive video environment is disclosed. The claimedembodiment comprises, inter alia, receiving a request from a clientdevice for playing a particular immersive video asset, wherein eachvideo frame comprises an array of tiles projected on a 3-dimensional(3D) display environment viewed by a user operating the client device. Aplurality of video tiles of the particular immersive video asset may beselected for assembling as a video frame for delivery to the clientdevice. In one arrangement, the selected plurality of video tiles of theparticular immersive video asset may be obtained from one or moretile-encoded bitrate representations of the particular video asset, eachbitrate representation having a separate video quality. A portion orsubset of the video tiles may be identified that can be replaced with acorresponding set of advertisement content tiles. Responsive thereto,the identified subset of the video tiles may be replaced with thecorresponding set of advertisement content tiles at specific locationswithin the video frame to be assembled. The video tiles as well as theadvertisement content files may be provided to a stream generator forassembling the video frame including the advertisement content tiles atselect locations, whereupon the assembled video frame may be transmittedto the client device. In one variation, the video tiles for replacementmay be identified based on a tile metadata specification that identifiesavailability information for each video tile. In another variation, thevideo tiles for replacement may be identified based on the gaze vectorinformation received from the client device. In a still furthervariation, the video tiles for replacement may be identified based on acombination of gaze vector information and tile metadata specification.In one implementation, the tile availability information (e.g., when atile may become available for replacement by a secondary content tile)may comprise or based on timing data involving least one of presentationtimestamp (PTS) information, decoding timestamp (DTS) information,program clock reference (PCR) information, system clock reference (SCR)information, a wall clock reference information, a Global PositioningSystem (GPS) timing reference information, and a runtime referenceinformation with respect to the particular immersive video asset beingplayed.

In a still further variation, the gaze vector information may beobtained by tracking an orientation of the user's headset associatedwith the client device for displaying the particular immersive videoasset. In another variation, the gaze vector information may be obtainedby tracking a movement of the user's eyeballs with respect to differentportions of the 3D display environment while the particular immersivevideo asset is being displayed. Regardless of how the gaze vectors areobtained, they may comprise, without limitation,normalized/non-normalized Cartesian coordinate vectors,normalized/non-normalized spherical coordinate vectors, or vectorsdefined in a suitable 3D geometrical coordinate system, and the like.

In another aspect, an embodiment of a video server system operative inassociation with a 360-degree immersive video streaming environment isdisclosed, which comprises one or more processors and one or morepersistent memory modules having program instructions thereon that areconfigured to perform an embodiment of the foregoing advertisementinsertion method when executed by the processor(s) of the system.

In a still further aspect, an embodiment of a client device operative ina 360-degree immersive video environment is disclosed, which comprisesone or more processors, a media player having user controls, and one ormore persistent memory modules having program instructions thereon thatare configured to perform when executed by the processors an embodimentof a device-based video playback method as set forth hereinbelow.

In an example implementation, a client device may be configured tooperate with various types of coded bitstreams having differentqualities that may be generated based on at least one of High EfficiencyVideo Coding (HEVC) H.265 compression, Alliance for Open Media (AOMedia)Video 1 (AV1) compression and H.266 compression, also referred to asVersatile Video Coding (WC) or Future Video Codec (FVC) compression.

In still further aspects, one or more embodiments of a non-transitorycomputer-readable medium or distributed media containingcomputer-executable program instructions or code portions stored thereonare disclosed for performing one or more embodiments of the methods ofthe present invention when executed by a processor entity of a networknode, apparatus, system, network element, subscriber device, and thelike, mutatis mutandis. Further features of the various embodiments areas claimed in the dependent claims.

Example embodiments disclosed herein provide several benefits in animmersive media consumption environment including but not limited to theability to insert various types of ad content that are not only morecoherent with the 360-degree video but are also configured to be placedin a video frame such that they don't hinder the immersive experienceregardless of the projection mapping scheme used in creating the 3Dspatial effect. Because the ads are embedded within the video and notoverlaid, an example ad insertion scheme of the present invention ismore resilient against ad blocking. Further, as the ad content tiles arestitched into a muxed frame according to standard video codectechniques, no extra decoder is need for playout by the clients.Additionally, content producers or editors can specify and controlcertain regions within a video where such ads can or cannot be placed byappropriately setting or configuring insertion policies.

In additional aspects, tiled video frames of a 360° immersive videoasset may be advantageously assembled with a subset of tiles optimizedfor higher quality viewports based on gaze vector information andallocated bandwidth. Because the frames are selectivelyviewport-optimized, transport of high quality multiplexed streams ispossible even in bandwidth-constrained environments without sacrificingthe viewing experience. Example embodiments may be advantageouslyconfigured such that the highest quality tiles will always be deliveredin the direct view, with controlled degrading qualities across multipleareas farther from the direct field of vision with the lowest quality inthe area that is in the diametrically opposite direction of where theuser is looking. Accordingly, when a stream is delivered to the device,the user always gets the highest video QoE in the area that they aredirectly looking at. Further, when the user moves their head, mid-GOPswitching facilitated by some example embodiments allows receiving highquality tiles as quickly as possible with minimal latency. With thetiles encoded for gradual refresh, when a user changes their field ofvision, example embodiments can further reduce the latency of the videoas the size of the video buffer may be minimized by sending several highquality tiles in the initial upgrade of the next frame to deliver. Overthe course of the next several frames, an example embodiment graduallyincreases the quality of the remaining tiles until the quality of tilesis reached based on the current field of vision and allowed bandwidth.

Additional benefits and advantages of the embodiments will be apparentin view of the following description and accompanying Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure are illustrated by way of example,and not by way of limitation, in the Figures of the accompanyingdrawings in which like references indicate similar elements. It shouldbe noted that different references to “an” or “one” embodiment in thisdisclosure are not necessarily to the same embodiment, and suchreferences may mean at least one. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

The accompanying drawings are incorporated into and form a part of thespecification to illustrate one or more exemplary embodiments of thepresent disclosure. Various advantages and features of the disclosurewill be understood from the following Detailed Description taken inconnection with the appended claims and with reference to the attacheddrawing Figures in which:

FIG. 1 depicts a generalized example network environment wherein one ormore embodiments of the present invention may be practiced for providing360° immersive video over a variety of network configurations;

FIG. 2 depicts an example network architecture comprising a portion ofthe environment shown in FIG. 1 for facilitating optimized tile encodingof 360° immersive video according to an example embodiment;

FIG. 3 depicts a block diagram of an example tile encoder that may beprovided as part of a media preparation and/or processing systemconfigured to operate in an arrangement of the network architecture ofFIG. 2;

FIGS. 4A-4C illustrate example video frames containing one or moreslices and/or tiles per each frame in an example encoder arrangement;

FIG. 5 is a flowchart illustrative of various blocks, steps and/or actsof a media preparation/processing method that may be (re)combined in oneor more arrangements, with or without blocks, steps and/or acts ofadditional flowcharts of the present disclosure, for facilitatingoptimized 360° immersive video according to one or more embodiments ofthe present invention;

FIG. 6 is illustrative of various blocks, steps and/or acts of anexample encoding arrangement involving either a Phased Encoding (PE)scheme or a Block-Intra Encoding (BIE) scheme that may be implemented aspart of the example media preparation/processing method of FIG. 5according to one or more embodiments of the present invention;

FIG. 7 is a flowchart illustrative of a BIE scheme according to anexample embodiment of the present invention;

FIG. 8A is a flowchart illustrative of a process for configuring a BIEscheme in a tiled encoding arrangement according to an exampleembodiment of the present invention;

FIG. 8B is a flowchart illustrative of additional blocks, steps and/oracts in an example BIE scheme according to an example embodiment of thepresent invention;

FIG. 9 is a flowchart illustrative of a PE scheme according to anexample embodiment of the present invention;

FIG. 10A is a flowchart illustrative of a process for configuring a PEscheme in a tiled encoding arrangement according to an exampleembodiment of the present invention;

FIG. 10B is a flowchart illustrative of additional blocks, steps and/oracts in an example PE scheme according to an example embodiment of thepresent invention;

FIG. 11 depicts a plurality of coded bitstreams having differentqualities generated by a BIE-based tiled encoder system in an exampleembodiment;

FIG. 12 depicts a plurality of coded bitstreams having different phasesfor a particular bitrate representation generated by a PE-based tiledencoder system in an example embodiment;

FIG. 13A is illustrative of various blocks, steps and/or acts of anexample tile stitching scheme involving BIE-based tiled streamsaccording to an embodiment of the present invention;

FIG. 13B is illustrative of various blocks, steps and/or acts of anexample tile stitching scheme involving PE-based tiled streams accordingto an embodiment of the present invention;

FIG. 13C is a flowchart illustrative of additional blocks, steps and/oracts with respect to an example tile stitching scheme according to anembodiment of the present invention;

FIG. 14 is illustrative of a 360° video frame comprising tiles selectedfrom coded bitstreams having different qualities or QPs in accordancewith an example embodiment of the present invention;

FIGS. 15A and 15B are flowcharts illustrative of various blocks, stepsand/or acts of a method that may be (re)combined in one or morearrangements, with or without blocks, steps and/or acts of additionalflowcharts of the present disclosure, for facilitating optimized tileselection based on weights associated with user gaze in a 360° immersivevideo viewing environment according to one or more embodiments of thepresent invention;

FIGS. 16A and 16B are illustrative of example geometrical arrangementsfor facilitating determination of angular separation between a user'sgaze direction and tile positions in a tile encoded frame;

FIG. 16C is illustrative of an example 360° immersive video viewingenvironment for purposes of one or more embodiments of the presentinvention;

FIG. 17A is a flowchart illustrative of additional blocks, steps and/oracts with respect to an example 360° immersive video optimizationprocess according to an example embodiment of the present invention;

FIG. 17B is a flowchart illustrative of additional blocks, steps and/oracts with respect to further aspects of an example 360° immersive videooptimization process according to an example embodiment of the presentinvention;

FIG. 18A depicts an example video frame having tile locations withdifferent weights determined in accordance with an embodiment of thepresent invention;

FIG. 18B depicts an example device buffer with frames ofdifferently-coded viewport tiles;

FIGS. 18C and 18D illustrate 3D viewing spaces where tile qualities aredistributed based on user gaze direction;

FIG. 19 is a flowchart illustrative of various blocks, steps and/or actsof a tile selection and bandwidth annealing process that may be(re)combined in one or more arrangements of a mediapreparation/processing method, with or without blocks, steps and/or actsof additional flowcharts of the present disclosure, according to one ormore embodiments of the present invention;

FIG. 20 is a flowchart illustrative of additional blocks, steps and/oracts with respect to an example tile selection and bandwidth annealingprocess according to an embodiment of the present invention;

FIGS. 21A and 21B are flowcharts illustrative of additional blocks,steps and/or acts with respect to further aspects of a tile selectionand bandwidth annealing process according to an example embodiment ofthe present invention;

FIG. 22 is illustrative of a transmit buffer model configuration for usea tile selection and bandwidth annealing arrangement according to anexample embodiment of the present invention;

FIG. 23 depicts an arrangement where a UE device may be configured toperform certain aspects of 360° immersive video optimization forpurposes of an embodiment of the present patent disclosure;

FIG. 24 depicts a block diagram of an apparatus that may be(re)configured and/or (re)arranged as a platform, node or element toeffectuate one or more aspects of 360° immersive video processing,preparation and optimization according to an embodiment of the presentinvention;

FIG. 25 depicts is a block diagram of an example UE device withadditional details for purposes of an embodiment of the present patentdisclosure;

FIGS. 26A-26C depict flowcharts illustrative of various blocks, stepsand/or acts relative to inserting advertisement content in a 360°immersive video asset during playout according to one or moreembodiments of the present invention;

FIG. 27 depicts an example tile metadata or manifest specificationoperative to indicate advertisement insertion availability for tiles ina video frame according to an embodiment of the present invention;

FIGS. 28A-28C depict example display scenarios with respect to insertingadvertisement content in a 360° immersive video environment according toan embodiment of the present invention;

FIG. 29 depicts a system for facilitating advertisement insertion in a360° immersive video environment; and

FIG. 30 is a flowchart of various blocks, steps and/or acts relative torelative to inserting advertisement content in a 360° immersive videoasset during playout according to further embodiments of the presentinvention.

DETAILED DESCRIPTION

In the description herein for embodiments of the present invention,numerous specific details are provided, such as examples of componentsand/or methods, to provide a thorough understanding of embodiments ofthe present invention. One skilled in the relevant art will recognize,however, that an embodiment of the invention can be practiced withoutone or more of the specific details, or with other apparatus, systems,assemblies, methods, components, materials, parts, and/or the like. Inother instances, well-known structures, materials, or operations are notspecifically shown or described in detail to avoid obscuring aspects ofembodiments of the present invention. Accordingly, it will beappreciated by one skilled in the art that the embodiments of thepresent disclosure may be practiced without such specific components. Itshould be further recognized that those of ordinary skill in the art,with the aid of the Detailed Description set forth herein and takingreference to the accompanying drawings, will be able to make and use oneor more embodiments without undue experimentation.

Additionally, terms such as “coupled” and “connected,” along with theirderivatives, may be used in the following description, claims, or both.It should be understood that these terms are not necessarily intended assynonyms for each other. “Coupled” may be used to indicate that two ormore elements, which may or may not be in direct physical or electricalcontact with each other, co-operate or interact with each other.“Connected” may be used to indicate the establishment of communication,i.e., a communicative relationship, between two or more elements thatare coupled with each other. Further, in one or more example embodimentsset forth herein, generally speaking, an element, component or modulemay be configured to perform a function if the element may be programmedfor performing or otherwise structurally arranged to perform thatfunction.

As used herein, a network element, node or subsystem may be comprised ofone or more pieces of service network equipment, including hardware andsoftware that communicatively interconnects other equipment on a network(e.g., other network elements, end stations, etc.), and is adapted tohost one or more applications or services, either in avirtualized/non-virtualized environment, with respect to a plurality ofsubscribers and associated user equipment (UE) nodes that are operativeto receive/consume content in a media distribution network where mediacontent assets may be distributed and delivered using stream-based orfile-based mechanisms. As such, some network elements may be disposed ina wireless radio network environment whereas other network elements maybe disposed in a public packet-switched network infrastructure,including or otherwise involving suitable content delivery network (CDN)infrastructure that may comprise public, private, or mixed CDNs.Further, suitable network elements including one or more embodiments setforth herein may involve terrestrial and/or satellite broadband deliveryinfrastructures, e.g., a Digital Subscriber Line (DSL) networkarchitecture, a Data Over Cable Service Interface Specification(DOCSIS)-compliant Cable Modem Termination System (CMTS) architecture,switched digital video (SDV) network architecture, a HybridFiber-Coaxial (HFC) network architecture, a suitable satellite accessnetwork architecture or a broadband wireless access network architectureover cellular and/or WiFi connectivity. Accordingly, some networkelements may comprise “multiple services network elements” that providesupport for multiple network-based functions (e.g., 360° immersive A/Vmedia preparation delivery policy management, session control, QoSpolicy enforcement, bandwidth scheduling management, content providerpriority policy management, streaming policy management, and the like),in addition to providing support for multiple application services(e.g., data and multimedia applications including 360° immersive videoassets (also referred to as 360-degree video assets or simply 360 videoassets) in varying qualities or definitions). Example subscriber endstations or client devices may comprise various devices, tethered oruntethered, that may consume or deliver media content assets usingstreaming and/or file-based downloading technologies, which may involvesome type of rate adaptation in certain embodiments. Illustrative clientdevices or UE devices may therefore include any device configured toexecute, inter alia, one or more client applications for receiving,recording, storing, and/or decoding/rendering 360 video content, livemedia and/or static/on-demand media, which may comprise Virtual Reality(VR) media, Augmented Reality (AR) media, Mixed Reality (MR) media, fromone or more content providers, e.g., via a broadband access network,using HTTP, HTTPS, RTP, and the like. Accordingly, such client devicesmay include Next Generation IP-based STBs, networked TVs,personal/digital video recorders (PVR/DVRs), networked media projectors,portable laptops, netbooks, palm tops, tablets, smartphones,multimedia/video phones, mobile/wireless user equipment, portable mediaplayers, portable gaming systems or consoles (such as the WHO, PlayStation 3®, etc.) operating in concert with 3D display devices and thelike, which may access or consume 360-degree content/services providedvia a suitable media distribution network wherein a bandwidth andQuality of Experience (QoE) scheme may be provided in accordance with toone or more embodiments set forth herein.

One or more embodiments of the present patent disclosure may beimplemented using different combinations of software, firmware, and/orhardware. Thus, one or more of the techniques shown in the Figures(e.g., flowcharts) may be implemented using code and data stored andexecuted on one or more electronic devices or nodes (e.g., a subscriberclient device or end station, a network element, etc.). Such electronicdevices may store and communicate (internally and/or with otherelectronic devices over a network) code and data using computer-readablemedia, such as non-transitory computer-readable storage media (e.g.,magnetic disks, optical disks, random access memory, read-only memory,flash memory devices, phase-change memory, etc.), transitorycomputer-readable transmission media (e.g., electrical, optical,acoustical or other form of propagated signals—such as carrier waves,infrared signals, digital signals), etc. In addition, such networkelements may typically include a set of one or more processors coupledto one or more other components, such as one or more storage devices(e.g., non-transitory machine-readable storage media) as well as storagedatabase(s), user input/output devices (e.g., a keyboard, a touchscreen, a pointing device, and/or a display), and network connectionsfor effectuating signaling and/or bearer media transmission. Thecoupling of the set of processors and other components may be typicallythrough one or more buses and bridges (also termed as bus controllers),arranged in any known (e.g., symmetric/shared multiprocessing) orheretofore unknown architectures. Thus, the storage device or componentof a given electronic device or network element may be configured tostore code and/or data for execution on one or more processors of thatelement, node or electronic device for purposes of implementing one ormore techniques of the present disclosure.

Referring now to the drawings and more particularly to FIG. 1, depictedtherein is a generalized example network environment 100 where one ormore embodiments of the present invention may be practiced for providingimmersive video distributed over a variety of configurations forconsumption by one or more viewing devices. An example videosource/capture system 102 is illustrative of any arrangement configuredto record, generate, read, decode, provide, or otherwise obtain mediathat is renderable for 360° viewing in myriad client deviceenvironments, which may include tethered or untethered devices,standalone pieces of equipment, subscriber premises equipment, gamingequipment, and/or equipment operating in paired combination(s) with 3Ddisplay devices, etc., operating with a variety of access/connectiontechnologies, as noted elsewhere in the present patent application. Byway of illustration, computers/displays 144, which may be associatedwith head-mounted displays (HMDs) or headsets 142, which may in turnalso be associated with portable devices such as tablets, smartphones,phablets, gaming devices, etc., collectively shown as devices 140, andthe like, generally shown as client devices 138, may be configured todecode and render various types of 360° video content that may beencoded and bandwidth-optimized according to the teachings of thepresent invention as will be set forth in additional detail furtherbelow. In one embodiment, example 360° immersive video source/capturesystem 102 may comprise one or more high-definition cameras (e.g., 4K,8K, etc.), including omnidirectional or panoramic cameras, etc. or avideo storage that may be configured to provide source video streams ina number of ways. Depending on the configuration and level ofintegration with respect to video preprocessing, output streams fromexample 360° immersive video source/capture 102 may be provided asstreams compatible with one or more interfaces, High DefinitionMultimedia Interface (HDMI), Serial Digital Interface (SDI), HighDefinition SDI (HD-SDI), or other formats, which may comprise unstitchedor stitched streams, with or without projection-mapping, and with orwithout source video encoding. For example, unstitched source streamswithout projection mapping 104A may be provided to a video stitcher 106that combines streams covering overlapping angles into a stitched stream108. In another embodiment, video source steams may comprise stitchedHDMI/SDI/HD-DSI streams 104B. Also, there may be other processing ofcaptured video that may involve les correction. Where the streams arenot projection-mapped, a projection mapping system 110 is operative togenerate a projection-mapped steam 114 from stitched streams 104B/108using a suitable map projection scheme, e.g., a spherical imageprojection including, without limitation, equirectengular projection,Cube Map projection, Equi-Angular Cubemap (EAC) projection, Pyramidprojection, Fish-Eye projection, etc. In a still further embodiment,video streams may comprise stitched and projection-mapped streams 104Cthat may be provided to a source video encoding module 112 operative toeffectuate one or more encoding or compression schemes depending onimplementation, e.g., including, without limitation, H.264 or AdvancedVideo Coding (MPEG-4 AVC), High Efficiency Video Coding (HEVC) or H.265(MPEG-H Part 2), H.262 (MPEG-2), H.264 (MPEG-4, Part 2), Alliance forOpen Media (AOMedia) Video 1 (AV1), H.266, Versatile Video Coding (VVC),Future Video Coding (FVC), etc., where some of the schemes may or maynot include tile encoding and/or may or may not adaptive bitrate (ABR)transcoding. In one arrangement, projection-mapped streams from theprojection mapping system 110 may also be provided to the encoder system112 for effectuating appropriate video compression. Depending on theconfiguration and the level of integration with respect to preprocessingin media preparation, a tiled encoder/transcoder 120 is advantageouslyprovided in accordance with the teachings of the present invention toprocess uncompressed video streams received from the projection mappingsystem 110 (video streams 114), compressed video streams received fromthe encoder system 112 (video streams 116), or video streams 104C fromthe video source/capture system 102. As will be set forth in furtherdetail below, tiled encoder/transcoder 120, whose functionality may beintegrated with the encoder system 112 and/or the projection mappingsystem 110 in some embodiments, is operative to generate encoded streamsof multiple bitrate representations of an input video streamcorresponding to a 360° immersive video asset or program, wherein eachbitrate representation having a certain video quality level may beencoded to contain frames with appropriately modified tile, frame and/orslice data to facilitate bandwidth-optimized 360° video distribution. Atiled packager 122 is operative to package the encoded streams fromencoder/transcoder 120 for storage 124 and provide associated manifestfiles 126 describing tile groupings, tile locations, media types andrelated characteristics of the encoded streams. As will be further setforth below, a tile selection and stream generation system 132 isoperative to select appropriate tiles responsive to control inputs andgenerate a multiplexed video output stream that may be delivered by adelivery server 134 associated with an access network 136 serving theviewing devices 138. In an example implementation, delivery of themultiplexed video streams to end users may be effectuated based on anumber of protocols, e.g., HTTP/S, chunked HTTP/S, RTP/RTCP, etc., overa variety of network infrastructures, as noted elsewhere in the presentpatent application.

Skilled artisans will recognize that the foregoing generalized examplenetwork environment 100 may be implemented in a hierarchical networkarchitecture, with various aspects of media capture and preparation,including, e.g., source stream stitching, projection mapping, sourcemedia compression, tiled/ABR encoding/transcoding, packaging, etc., aswell as distributing/uploading and edge node processes taking place indifferent network portions disposed at different hierarchical levels,involving one or more operators, content delivery networks (CDNs), edgenetworks, and the like. Further, in some implementations, at least someof the foregoing apparatuses and processes may be cloud-based. In somearrangements, a CDN can be a large distributed system of serversdeployed in multiple data centers connected to the Internet or otherpublic/private communications network. A CDN can be a managed orunmanaged network, and can also be a federation of managed or unmanagednetworks.

An example embodiment of a media server/source system operativelyassociated within the foregoing example network environment maytherefore be configured, e.g., as a global headend, to accept mediacontent from live sources and/or static file sources, e.g., onlinecontent providers such as Hulu®, Netflix®, YouTube®, or Amazon® Prime,as well as VOD catalog or content providers or studios such as, e.g.,Disney, Warner, Sony, etc. Media content from live sources may compriselive programming captured relative to any type of event, e.g.,sporting/entertainment/gaming events, concerts, live TV shows, live newsbroadcasting sources, such as, for instance, national broadcasters(e.g., NBC, ABC, etc.) as well as cable broadcaster channels like TimeWarner channels of CNN, ESPN, CNBC, etc., and local broadcasters, etc.,including any secondary media insertions such as advertisement mediachannels.

Without limitation, an example network architecture 200 (which may forma portion of the environment shown in FIG. 1) is depicted in FIG. 2 forfacilitating optimized tile encoding of immersive video according to anembodiment of the present invention. A media input stream 202 isillustrative of a video stream corresponding to a 360° video asset thatmay be suitably stitched, projection-mapped and/or encoded as set forthin FIG. 1, which may be distributed, uploaded or otherwise provided to aCDN origin server 204 associated with an operator content deliverynetwork 206. Broadly, media input stream 202 may comprise a streamcorresponding to least one of live TV content, IPTV content,time-shifted (TS) TV content, place-shifted (PS) TV content, gamingcontent, Video on Demand (VOD) content, VR/AR/MR content, networkeddigital video recorder (nDVR) content, and the like, or any content thatis (pre)processed for 360-degree viewing experience. A CDN edge server208 coupled to CDN 206 may be configured to receive the uploaded mediastream(s) 202 corresponding to respective video assets, which may bestored in suitable database(s) (not specifically shown). A tiled encoder210, which may be configured to operate in compliance with a standardcodec scheme (e.g., HEVC, AV1, etc.) is operative to generate aplurality of tiled adaptive bitrate streams 212 where each stream maycomprise tiles of a specific resolution, bitrate, and pixel sizes(depending on aspect ratios). By way of illustration, steams 212 maycomprise one or more 32K streams (30730 horizontal pixels×17280 verticalpixels), 16K streams (15360 horizontal pixels×8640 vertical pixels), oneor more 8K streams (7680 horizontal pixels×4320 vertical pixels), one ormore 4K streams (3840 horizontal pixels×2160 vertical pixels), one ormore HD streams (1920 horizontal pixels×1080 vertical pixels), one ormore 720p streams (1280 horizontal pixels×720 vertical pixels), etc.,wherein higher resolution streams may be encoded at higher bitrateranges while lower resolution streams may be encoded at lower bitrateranges. For instance, 32K streams may be encoded in the range of800-1000 Mbits/s (or Mbps), 16K streams may be encoded in the range of200-300 Mbps, 8K streams may be encoded in the range of 80 to 100 Mbps,and so on to 720p streams encoded in the range of 1.2 to 3 Mbps.Further, tiled adaptive bitrate streams 212, also referred to astile-encoded bitstreams, may comprise frames having a suitable number oftiles per frame, e.g., 128 tiles for 4K, depending on the scheme beingemployed.

In one arrangement, tiled encoder 210 may be configured to generatetiled-encoded bitstreams as a plurality of phase-encoded streams foreach bitrate representation of the media input stream 202, wherein eachphase-encoded stream for a particular bitrate representation is providedwith a specialized frame at a particular location in theGroup-of-Pictures (GOP) structure of the stream depending on the phaseas will be set forth in additional detail further below. This scheme ofencoding may be referred to as Phased Encoding (PE) scheme with respectto certain embodiments of present invention. In another arrangement,tiled encoder 210 may be configured to generate a pair of tiled-encodedbitstreams, e.g., a first and a second tile-encoded bitstream, for eachbitrate representation of the media input stream 202, wherein a firstencoded bitstream may comprise a regular or standard tile-codedbitstream generated according to a known or heretofore unknown codingscheme and a second encoded bitstream may be coded such that aspecialized frame is provided at each location in a GOP structure, aswill be set forth in additional further below. This scheme of encodingmay be referred to as Block-Intra Encoding (BIE) or All-Intra Encoding(AIE) scheme with respect to certain embodiments of the presentinvention.

Regardless of whether PE-coding scheme or BIE-coding scheme is used, apackager 214 is operative to package the tile-encoded bitstreams 212 andgenerate suitable manifest files describing characteristics of tilegroupings per frame for each tile-encoded bitstream, e.g., tilelocation, slice header information, various types of metadata includingpicture timing, color space information, video parametric information,etc., which may be stored at a suitable packaged media storage facility240, along with suitable stream manifests 241. A network edge node 216including a video optimization system 215 comprising a plurality ofmodules or subsystems is operative in association with a video backoffice system 238 for effectuating a 360° immersive video session with apremises device 236 of subscriber premises 234 that is served by amanaged bandwidth pipe 232 effectuated via a suitable access network(e.g., a DSL/DOCSIS network portion having suitable infrastructure thatmay include, e.g., routers, DSLAM/CMTS elements, etc., or suitable3G/4G/5G radio access network elements, including fixed wirelessinfrastructure in certain implementations, and the like), generallyrepresented by node or element 230.

In one arrangement, video optimization system 215 may comprise a tileselection subsystem 218 that is operative responsive to bandwidthannealing and QoE management policies, as well as user gaze vectorinformation, inter a/ia, to provide tiles 220 selected from differentvideo quality bitstreams to a tile combining and stream generationsubsystem 222. Multiplexed video frames with tiles from differentbitstreams 224 may be provided to a delivery service 226 forfacilitating the transmission of muxed tile stream 228 to the downstreaminfrastructure 230. Broadly, when a user request 250 for a 360°immersive video session is generated, it is processed by the video backoffice system 238 and forwarded to the video optimization system 215 viaa message 252 for obtaining a session ID and associated locationinformation for the requested 360° media. Responsive to a responsemessage 251 from the video optimization system 215, the video backoffice system 238 is operative to provide a response 248 includingappropriate URL information for the media and a session ID to therequesting device 236. User gaze information (which may be a defaultsetting initially) and associated session ID information may be providedto the infrastructure element 230 as a message 246, which may bepropagated to the video optimization system 215 as message 254. Also,the infrastructure element 230 is operative to provide a dynamicbandwidth allocation message 254 that includes the session IDinformation to the video optimization system 215 in a related orseparate process. As noted previously, tile selection subsystem 218 maybe configured to operate in response to control messages relative tobandwidth allocation, user gaze vector information, or both, forselecting tiles having different video qualities, which may be combinedor stitched into frames in order to generate a muxed tile-encoded videooutput stream. In one arrangement, the tile combining and streamgeneration subsystem 222 may be provided as part of the videooptimization system 215 during video stream delivery. In anotherarrangement, the tile stitching may be effectuated during playout on theclient side (e.g., at the client device 236 or some other premisesequipment associated therewith) rather than on the server side. In thisarrangement, a client-side stitching functionality is operative toreceive the selected tiles and perform the necessary stitching in orderto generate a stitched stream to be decoded and rendered. Variousembodiments relative to the foregoing processes, subsystems andcomponents will be set forth in further detail in the followingsections.

FIG. 3 depicts a block diagram of an example tile encoder 300 that maybe provided as part of a media preparation and/or processing systemconfigured to operate within an arrangement of the network architectureof FIG. 2. Without limitation, example tile encoder 300 will be setforth below that may be configured to effectuate either a PE codingscheme or a BIE coding scheme for generating multi-bitrate video streamshaving different qualities with respect to each media asset while beingcompliant with known or heretofore unknown standard codec schemes, suchas, e.g., H.265, H.266, VVC, AV1, etc., that are compatible with tileencoding. Broadly, in one embodiment, a specialized frame (or, somewhatsynonymously, a picture) is generated that is encoded as apredictive-coded (P) picture or frame (i.e., having a header identifyingit as a P-frame) but only contains coding blocks or units that areencoded as intra-coded blocks or units (i.e., I-blocks). In anotherembodiment, a specialized frame may comprise a frame identified as abi-predictive (B) frame but contains only I-blocks. For purposes of thepresent patent application, these specialized frames are referred to as“block-intra” frames or “X” frames, where media image data of all theblocks are forced to be coded as intra-coded (i.e., no temporalestimation or prediction).

For purposes of example embodiments herein, a GOP structure is a groupof successive pictures in a coded video stream, which specifies theorder in which intra- and inter-frames are arranged. Each coded videostream comprises successive GOPs, from which the visible frames may begenerated. Generally, a GOP structure may contain the following picturetypes: (1) I-picture or I-frame (intra coded picture)—a picture that iscoded independently of all other pictures. Each GOP begins (in decodingorder) with this type of picture. (2) P-picture or P-frame (predictivecoded picture)—contains motion-compensated difference informationrelative to previously decoded pictures. In older designs such asMEPG-1, H.262/MPEG-2 and H.263, each P picture can only reference onepicture, and that picture must precede the P picture in display order aswell as in decoding order and must be an I or P picture. Theseconstraints do not apply in the newer standards such as, e.g.,H.264/MPEG-4 AVC, H.265/HEVC, etc. (3) B-picture or B-frame(bi-predictive coded picture or bidirectionally predictive codedpicture)—which contains difference information from the preceding andfollowing I- or P-frame within a GOP, and contains motion-compensateddifference information relative to previously decoded pictures. In olderdesigns such as MPEG-1 and H.262/MPEG-2, each B-picture can onlyreference two pictures, the one which precedes the B picture in displayorder and the one which follows, and all referenced pictures must be Ior P pictures. These constraints do not apply in the newer standardssuch as, e.g., H.264/MPEG-4 AVC, H.265/HEVC, etc. (4) D-picture orD-frame (DC direct coded picture)—serves as a fast-access representationof a picture for loss robustness or fast-forward in certain types ofvideo (e.g., MPEG-1 video).

In general, an I-frame indicates the beginning of a GOP. Afterwardsseveral P and B frames may follow. The I-frames contain the full imageand do not require any additional information to reconstruct it.Typically, encoders use GOP structures that cause each I-frame to be a“clean random access point,” such that decoding can start cleanly on anI-frame and any errors within the GOP structure are corrected afterprocessing a correct I-frame. The GOP structure is often referred by twonumbers, for example, M=3, N=12. The first number tells the distancebetween two anchor frames (I or P). The second one tells the distancebetween two full images (I-frames), which is the GOP size. For theexample M=3, N=12, the GOP structure is {IBBPBBPBBPBBI}. Instead of theM parameter the maximal count of B-frames between two consecutive anchorframes can be used. For example, in a sequence with pattern{IBBBBPBBBBPBBBBI}, the GOP size is equal to 15 (length between two Iframes) and distance between two anchor frames (M value) is 5 (lengthbetween I and P frames or length between two consecutive P Frames).

While a typical GOP starts with an I-frame, some embodiments hereinprovide a structure where a GOP may commence with an X-frame instead, inaddition to placing the X-frames at specific locations or replacing theP- and/or B-frames in the GOP structure as will be set forth inadditional detail further below.

Skilled artisans will recognize that depending on codec implementation,a picture or frame may be partitioned into a number of ways at differentlevels of granularity, for example, to facilitate, inter alia, codingefficiency, parallel processing, etc. In one arrangement, a frame may bepartitioned into a number of coding tree units (CTUs), each containingcertain number of luma coding tree blocks (CTBs) and chroma CTBs, whichin turn may comprise multiple coding blocks (CBs). A frame may be splitinto one or more slices, each being a spatially distinct region of aframe that may be encoded separately from any other region in the sameframe and identified with a slice header. In general, slices areself-contained and contain a sequence of CTUs that are processed in theorder of a raster scan, wherein slices can be coded as I-slices,P-slices, or B-slices similar to I-frames, P-frames, or B-frames,respectively. In one arrangement, slices may be used to effectuateresynchronization to minimize data losses, and may contain a varyingnumber of CTUs per slice depending on the activity in a video scene.FIG. 4A illustrates an example video frame 400A containing a pluralityof slices 402-1 to 402-N, where an example slice 402-N contains a numberof CTUs 404.

In addition to slices, an encoding scheme may also define a number oftiles per frame, which may also be configured to be self-contained andindependently decodable rectangular or square regions of a picture,based on vertical and horizontal partitioning to form a grid, in orderto facilitate parallel processing at the encode and decode stages. Inone variant, the self-contained and independently decodable tiles mayuse temporal prediction from the co-located tiles of previously encodedpictures or frames. Multiple tiles may share header information by beingcontained in the same slice, where a tile may comprise a certain numberof CTUs. It is not a requirement that each tile include the same numberof CTUs. Accordingly, in one arrangement, the tiles of a frame may havedifferent sizes. If a frame contains a single slice, the tiles of theframe will therefore have the same slice header and picture headerinformation. In another arrangement, a frame may include one or moreslices, each slice containing one or more tiles, and each tile in turncontaining one or more CTUs. FIG. 4B illustrates an example video frame400B containing a plurality of CTUs, organized into a matrix or array oftiles 406-1 to 406-N, wherein each tile is shown as a square with 4 CTUs408 in a 2×2 configuration. By way of further illustration, an example4K video frame 400C according to HEVC is shown in FIG. 4C, which maycomprise an array of 3840 horizontal pixels by 2160 vertical pixels,that is partitioned into 16 columns and 8 rows, thereby resulting in 128tiles. As noted earlier, these tiles may not be necessarily sizedequally within the frame 400C.

For purposes of the present patent application, because video frames maybe partitioned in numerous ways and at different levels, the terms“coding tree unit”, “coding tree block”, “coding unit”, “macro block”,or “block” or terms of similar import will be generally treated as anabstract unit of coding that may applied with respect to a tile, sliceand/or frame without limitation to any particular video compressionstandard or technology.

Returning to FIG. 3, example tile encoder 300 may be configured withrespect to a PE- or BIE-based scheme to generate an X-frame where it iscoded as a P- or B-frame having the corresponding header but withindividual slices and/or tiles that are intra-coded, i.e., as I-slicesand/or I-tiles, comprising only I-blocks. In other words, the X-framesmay have header information of a P- or B-frame (or P-slice or B-slice ifonly one slice per frame is provided), but all the media image data isintra-coded as data of an I-frame. Remaining frames of a video sequencemay be encoded normally in accordance with a known or heretofore unknownscheme as noted previously. Accordingly, a general coder control 306 maybe configured to select between the PE and BIE schemes 308, 310 forproviding appropriate control signals and/or parameters to remainingcomponents and structures of a frontend portion 302 of the tile encoderso as to force the encoding of the special frames as needed according toa particular implementation of the PE or BIE schemes with respect to oneor more input video signals 304. In general, each picture in a PE schemeis either encoded as a regular I-frame (e.g., for the first picture in asequence) or as an X-frame for those input pictures that match thephase/period, and as regular P- or B-frames for all other pictures ofthe video sequence, as will be described in further detail below. Withrespect to the BIE scheme, a BIE-coded sequence may be provided whereX-frames are provided for all P- and B-frames of a GOP structure of thesequence. Accordingly, an intra/inter selection block 312 is configuredsuch that intra-picture estimation/prediction 316 is always active andused for all blocks of a picture. Likewise, motion compensation andestimation 318 may be disabled since all blocks are intra-coded for anX-frame. Remaining blocks comprising transform, scaling and quantization314, inverse transform 320, filter control 322, deblocking and sampleadaptive offset (SAO) filtering 324, decoded picture buffer 326 mayremain unaffected in an example embodiment depending on the tile encoderimplementation. General control data 328, quantized transformcoefficients data 330, intra prediction and filter control data 332 andmotion data 334 may be provided to a header formatter and entropyencoder 336 (e.g., a context-adaptive binary arithmetic coding (CABAC)engine) for generating one or more coded bitstreams 338 corresponding toeach bitrate representation of the video asset. As noted previously, thecoded bitstreams 338 may be provided to a tiled packager (not shown inthis FIG. 3) for packaging and manifest generation to facilitate(pre)provisioning of the assets at appropriate downstream networklocations.

FIG. 6 is illustrative of various blocks, steps and/or acts of anexample encoding arrangement 600 involving either a PE scheme or a BIEscheme that may be implemented as part of an example mediapreparation/processing according to an embodiment of the presentinvention. At block 604, a video source stream 602 is received, whichmay be unencoded, encoded, stitched, projection-mapped, or otherwisepre-processed, as previously described. At block 606, a determinationmay be made where PE or BIE is selected. A mode selector in a tileencoder system, e.g., tile encoder 300 in FIG. 3, may be appropriatelyconfigured in response. Upon selecting PE, the video source stream 602may be encoded/transcoded into a plurality of streams with differentqualities and/or bitrates, each being encoded with tiles, as set forthat block 608. Each quality or bitrate stream is phase-encoded togenerate a plurality of PE streams 610. By way of illustration,reference numeral 614-1 refers to quality information relating to a setof phase-encoded streams 612-1 with corresponding phases 615-1 to 615-P(depending on where an X-frame is placed in GOP structure, where P isthe GOP size), all PE streams having a Quantization Parameter (QP)setting of 30 and/or a bitrate of around 7.0 Mbits/s, which may beindicative of a lower end of quality. In similar fashion, referencenumeral 614-N refers to quality information relating to a set ofphase-encoded steams 612-N with corresponding phases 615-1 to 615-P, allhaving a QP setting of 16 and/or a bitrate of around 105.6 Mbits/s,which may be indicative of a higher end of quality.

If BIE (also referred to as All-Intra Encoding, as noted elsewhere inthe present patent application) is selected, the video source stream 602may be encoded/transcoded into a plurality of streams with varyingqualities and/or bitrates (block 616). In one example embodiment, eachof the streams may be tile-encoded using a standard coding scheme (e.g.,HEVC, AV1, etc.) to generate normal or regular tile-encoded streams 618.Similar to the discussion above with respect to the phased-tiled streams610, reference numeral 622-1 refers by way of illustration to qualityinformation relating to a regular tile-encoded stream 620-1 having a QPsetting of 30 and/or a bitrate of around 7.0 Mbits/s, which may beindicative of a lower end of quality. Likewise, reference numeral 622-Nrefers to quality information relating to a regular tile-encoded steam620-N having a QP setting value of 16 and/or a bitrate of around 105.6Mbits/s, which may be indicative of a higher quality stream.

Additionally, the video source stream 602 is also encoded/transcodedinto a plurality of streams with corresponding qualities and/or bitrates(block 617) where each stream is tile-encoded such that all frames ofit's GOP structure are provided as X frames. By way of illustration,reference numeral 632 refers to a plurality of BIE-coded and tiledstreams, wherein quality information 636-1 having a QP setting of 30and/or a bitrate of around 7.0 Mbits/s (also sometimes abbreviated asMbs or Mb/s) relates to a lower quality BIE-coded tiled stream 634-1while quality information 636-N of QP setting of 16 and/or a bitrate ofaround 105.6 Mbits/s relates to a higher quality BIE-coded tiled stream634-N.

Skilled artisans will recognize upon reference hereto that when anencoder is configured with a target QP, the bitrate of an encodedbitstream is somewhat averaged over the course of the bitstream. Forinstance, if a QP of 10 is targeted in a source encoding scheme, it ispossible that a low bitrate may be seen in areas of no motion (e.g.,resulting in 4 Mbs). In areas of high motion, it is possible that thebitrate could shoot up to 200 Mbs. Thus, in an example encoding schemethat targets specific QPs as set forth in the foregoing, the bitrates ofthe output steams could be variable over a range. Accordingly, it shouldbe appreciated that the bitrates shown in association with the QPs of PEor BIE streams in FIG. 6 are generally indicative of average bitratesover a course of time. As will be seen further below, when QPs aretargeted in an encoding scheme (with varying bitrates correspondingly),certain embodiments of the present invention relating to tile selectionmay be configured to select tiles and fit them in accordance with anoverall allocated bitrate with respect to a particular 360-degreeimmersive video session. In an additional or alternative embodiment, anexample encoder may be configured to generate coded bitstreams havingspecific target bitrates instead of target QPs. In such an arrangement,while an output bitstream may maintain a particular bitrate, the QPvalues may vary, however. An embodiment of tile selection may thereforeselect tiles based on video qualities that may be controlled bydifferent encoding parameters and settings and fit them accordingly tooptimize the allocated bandwidth. For purposes of the present patentapplication, the terms “quality”, “video quality”, and terms of similarimport with respect to coded bitstreams or bitrate representations maybe broadly related to and/or based on QPs, bitrates, other indicia.Thus, embodiments relating to PE/BIE encoding, tile selection, stitchingand the like set forth herein based on targeted QPs are also equallyapplicable to bitstreams having targeted bitrates, mutatis mutandis.

Accordingly, it should be understood by the reader that although certainexamples and portions of the description within this disclosure areprovided assuming the use of a fixed quantization (QP) value per stream,streams in practice may contain QP values that vary between pictures andwithin a picture as noted above. An encoder according to an embodimentof the present invention may control its output bitrate by the means ofa rate-control or the like, and thereby change the QP value betweenpictures. An encoder may also encode pictures within one stream usingvarying QP values to optimize the visual quality of the stream. Withinone picture, the QP value may change between blocks using e.g., adaptivequantization mechanisms to optimize the visual quality as known in theart. The use of “QP” in phrases within this disclosure such as e.g., butnot limited to, “encoded with that QP”, “video of different QP values”,“generated videos with different QP values”, “stream having a QP valueof N”, “QP value of the video stream” should be understood as a way ofcharacterizing streams such that a stream associated with a lower QPvalue is of higher bitrate and higher quality than one associated with ahigher QP value, and not that the QP is kept static for each block in astream.

It should be further appreciated that adaptive bitrate encoding and tileencoding of media assets may be integrated within an apparatus as partof a content preparation system in one example embodiment such thatvarious types of encoding and/or transcoding may take place in differentsequences and/or in parallel processes. Further, additionalfunctionalities such as projection-mapping, source stream stitching,packaging, etc., may also be combined or otherwise integrated with thetile-coding/transcoding schemes of the present patent applicationdepending on implementation.

FIG. 5 is a flowchart illustrative of various blocks, steps and/or actsof a method 500 that may be (re)combined in one or more arrangements,with or without blocks, steps and/or acts of additional flowcharts ofthe present disclosure, for facilitating optimized 360° immersive videoaccording to one or more embodiments of the present invention. At block502, various operations relative to media capture and preprocessing of amedia input stream for immersive video, e.g., source stream stitching,encoding, projection mapping, etc. may be effectuated. At block 504,adaptive-friendly bitrate encoding/transcoding of the preprocessed mediainput stream into multiple bitrate representations or streams havingdifferent video qualities (e.g., with varying QP values) may beeffectuated in association with a tiled encoding scheme. As notedpreviously, either a PE-based coding process (block 506B) or a BIE-basedcoding process (block 506A) may be configured to generate codedbitstream output. It should be noted that the processes of blocks 504and 506A/B could be executed as single encoding operations such that theadaptive-friendly bitrate encode/transcoding of block 504 is done usingeither a PE scheme (block 506A) or a BIE scheme (block 506B) using asingle encode process. Thereafter, the coded bitstreams may be packaged(block 508) and distributed to appropriate network edge locations (block510) for delivery and consumption by clients using suitable end userequipment. When a user request for a particular media asset is receivedand processed, a tile selection process based on control inputs e.g.,transmission conditions, bandwidth allocation and/or gaze vector input,etc., may be effectuated for selecting tiles from different bitraterepresentations (i.e., different qualities) of the media asset (block512). A stream generation process may be effectuated for stitching theselected tiles into frames as an output video stream to be delivered tothe requesting client device (block 514).

Skilled artisans will recognize that at least a portion of the foregoingsteps, acts or operations may comprise media preparation and(pre)provisioning with respect to one or more 360° immersive videoassets distributed in a network environment or architecture illustratedin FIGS. 1 and 2 described above. Turning to FIG. 7, additional detailsregarding a BIE scheme 700 according to an example embodiment of thepresent invention are set forth. At blocks 702 and 704, a media inputstream relative to a 360° immersive video asset is received andprocessed to generate multiple bitrate representations havingdifferent/separate qualities, e.g., each video quality related to orcontrolled by a corresponding targeted QP value used for each bitraterepresentation and/or targeted bitrate, or other indicia of respectivequality. Each bitrate representation is coded into a first codedbitstream comprising a plurality of frames with a specific GOPstructure, wherein each GOP starts with an I-frame followed by a set offrames including at least one P-frame or B-frame (block 706). Further,each bitrate representation is encoded into a second coded bitstreamcomprising a plurality of frames with a GOP structure that has a sizecoextensive with the size of the GOP structure of the first codedbitstream, wherein each GOP of the second coded bitstream starts with anI-frame followed by a plurality of X-frames, each X-frame being codedwith a slice/picture header of a P- or B-frame and comprisingintra-coded media image data only (i.e., similar to an I-frame of theGOP), as set forth at block 708. As noted previously, the first codedbitstream and the second coded bitstream may be encoded as respectivetile-encoded streams using any tile-compatible compression scheme,wherein each frame of the tile-encoded bitstream comprises an array oftiles organized into at least one slice per frame, each tile comprisinga portion of the media data of the frame formed as a number of codingunits, blocks or trees. One skilled in the art will recognize that inone implementation, processes of block 704 and 706 may be performed in asingle encode process as noted previously in respect of blocks 504 and506A/B of FIG. 5. For instance, in practice, a single processencoding/transcoding would be desirable to minimize the computationalcomplexity and minimize degradations introduced by tandem or cascadedencoding.

FIG. 11 depicts a plurality of coded bitstreams 1100 having differentqualities or QPs generated by a BIE-based tiled encoder system in anexample embodiment. Reference numerals 1102-1 to 1102-N refers to Nstreams or bitrate representations having corresponding qualities orQPs. A normally encoded tiled stream 1104A corresponding to a particularbitrate representation, e.g., QP-N 1102-N, is illustrated with a GOPstructure 1106A having four frames, starting with an I-frame followed bythree P-frames. Corresponding BIE-coded stream 1104B has a GOP structure1106B, which is also illustrated with four frames, starting with anI-frame but followed by three X-frames.

FIG. 8A is a flowchart illustrative of a process 800A for configuring aBIE scheme in a tiled encoding arrangement according to an exampleembodiment of the present invention. Without limitation, example process800A will be described in reference to configuring an HEVC scheme forperforming BIE based on modifying certain parameters, although otherschemes may also be applied for purposes herein.

In general, an embodiment of a BIE configuration method may beconfigured to receive or obtain as input a source video stream for 360°immersive video and a list of output video qualities (e.g., a list of QPvalues, such as {QP1=16, QP2=18, QP3=20, QP4=22, QP5=24, QP6=26, QP7=28,QP8=30, or other indicia based on targeted bitrates}). Accordingly,without limitation, for every output video quality (e.g., every QPvalue), two video streams may be encoded—a regular/standard HEVC videowith that QP or quality, and a Block-Intra HEVC video with thatQP/quality—as noted previously. In order to be able at a later time(e.g., shortly before decoding) to stitch tiles from different qualitiesinto the same bitstream, the encoding phase of an embodiment providesthat all the video streams have the same base_qp (defined below), whilethe actual difference between the videos of different QP values may beeffectuated by means of qp_delta (defined below) from the base QP. Forexample, a setting of base_qp=22 may be configured, wherein theparametric values base_qp=22 and qp_delta=−6 may be used to achieveQP=16. In general, these two parameters relate to setting the quality(QP) of a video stream. Recall that all the generated videos with thedifferent qp values need to have the same base_qp, while different QPvalues may be achieved by using qp_delta from the base_qp. Thisrequirement may be imposed based on one particular time instance. Thatis, if pictures in a bitstream are numbered, then any two pictures fromtwo bitstreams that are used as input for stitching with the samenumbers must use the same base_qp value in one arrangement. For purposesof the present invention, “base_qp” may be described as follows: thei^(th) frame (for every i=1 to N, where N is the total number of framesin a video sequence) in all the encoded versions or bitraterepresentations of the same video will have the same slice QP value. Inother words, slice QP is the base_qp. Although slice QP may be set asthe same value in all the generated streams, it can vary over time. Forpurposes of the present invention, the parameter delta_qp may bedescribed as follows: by assigning a given qp_delta, the first block ineach tile that signals QP is configured to signal the delta_qp (thatamount of variance from the base QP). It may be noted that there couldbe a deblocking mismatch after stitching in some embodiments.

Another parameter that may be defined for purposes of the presentinvention is ROI (Region of Interest), which determines an area of aframe where the tiles can be independently encoded so that the subset ofthe bitstream corresponding to the ROI can be easily extracted andreconstituted into another bitstream. As noted above, in order to laterstitch videos of different QPs, it is desirable to utilize thefunctionality of base_qp and delta_qp. This is supported for examplewhen using HEVC ROI encoding functionality in one illustrativeimplementation. Accordingly, when encoding with ROI in an embodiment,the base_qp parameter for the slice QP headers may be defined, inaddition to defining an ROI grid (independently defined from thegrid/array of the tiles of a frame) such that the area of the grid inthe i^(th) row and j^(th) column in the ROI grid gets its own delta_qp.Generally, this allows an embodiment to assign different delta_qp todifferent areas of the ROI grid, whereby selective delta_qp values maybe used for purposes of the present invention. For example, to achieve agiven desired QP (say QP=16), the base_qp may be defined (saybase_qp=22) using the regular qp parameter, and then by using the ROIgrid, all the targeted areas may be assigned a delta_qp of −6, thuseffectively achieving a QP of 16 for all the tiles in the ROI grid.

In one embodiment, the content at different qualities may be encodedusing the same base_qp (slice QP) for a particular frame. For eachquality of that frame, a specific desired QP may be set, wherein thedelta_qp syntax elements may be used so that all blocks (oralternatively, as many blocks as possible or desired) of that frame areencoded with that desired QP. Additional aspects of a BIE configurationscheme based on HEVC may be set forth as follows.

The encoder may be set to use tiled encoding. During setup, this may beeffectuated by setting an appropriate flag for tiled-encoding, as wellas configuring a specific grid structure of the tile (e.g., as shown inFIG. 4C). By way of illustration, the encoder may be configured toprovide a 16×8 grid structure of tiles, resulting with 128 tiles in eachframe, for a 4K video input.

The encoder may be configured to disable temporal motion vectorsprediction. Although an example BIE scheme does not use MVs (motionvectors), temporal motion vector prediction (TMVP) settings may need tobe identical across streams to enable stitching at a later time. Thisconfiguration is optional, in that an embodiment of BIE may be practicedwithout disabling TMVP.

Also, many other elements of the slice headers may be configured to beidentical across streams. For example, elements such as the number ofreference pictures to use, the reference picture set, what referencepictures to use for LO, the Picture Parameter Set (PPS) to use, thepicture order count, SAO parameters, etc. Further, it is also requiredthat the decoding order is the same for all bitstreams that are to beused as input for bitstream switching. Skilled artisans will recognizeupon reference hereto that a variety of slice header elements may beconfigured accordingly in an example BIE implementation.

Since a slice uses a single PPS id codeword to identify what PPS to useand the PPS references one single Sequence Parameter Set (SPS), allencodings may be done using identical PPS and SPS id values in anexample embodiment. Likewise, many syntax elements in the SPSs and PPSsmay also be configured to be identical for the multiple encodings.Although not a necessary requirement, an example BIE embodiment maytherefore be configured such that the encodings are effectuated usingidentical SPSs and PPSs. However, it is strictly necessary that someelements in the SPS and PPS are identical in certain arrangements.

Returning to FIG. 8A, example BIE configuration process 800A maycommence with initializing a mode selector of an encoder to select BIEfor encoding an input video stream as set forth hereinabove (block 802).At block 804, the encoder may be configured to use tiles in a particulargrid or array arrangement for each frame. At block 806, the base_qpparameter may be written in all slice QP headers of the encoded streams.To encode streams in different qualities (while having the samebase_qp), a qp_delta parameter may be configured as described above withrespect to each stream based on target QPs (block 808). For example, toachieve a target QP of 22 for a particular stream, a qp_delta of −10 maybe configured where base_qp is 32. At noted before, it is required thatall pictures with the same picture number to be used as an input forstitching must use the same base_qp value. Thus, in one embodiment, itis not a necessary requirement to set the same base_qp parameter in allthe stream headers. Spatial motion vector prediction may be configuredsuch that it is restricted within the tile only (block 810). That is,motion vectors are not allowed to cross tile boundaries in an exampleembodiment (i.e., only intra-tile prediction is allowed). This meansthat motion vectors are set such that no sample outside the boundariesof any co-located tile is read during motion compensation interpolationof the blocks inside a tile. An ROI grid may be configured for theencoder such that it uses the qp_delta information for encoding aparticular stream with respect to a specific region of the frames (block812). Further, TMVP may also be disabled (block 814) in an example BIEconfiguration process as set forth above.

It should be noted that whereas the foregoing BIE configuration process800A uses certain parameters, additional or alternative embodiments maybe practiced where a BIE scheme may be configured to utilize otherparameters in addition to and/or in lieu of the parameters exemplifiedin the flowchart of FIG. 8A.

FIG. 8B is a flowchart illustrative of additional blocks, steps and/oracts in an example BIE scheme 800B according to an embodiment of thepresent invention. In general, during BIE-based tiled coding, an encodermay be configured to effectuate several decisions. During encoding oftiles which are part of a P-frame, the encoder decides whether or not aparticular tile should be encoded using any motion vector and depend onthe previous frame, or whether it should be encoded in “intra” mode,where the tile is self-contained and is not dependent on any previousframe (i.e., does not use prediction from any previous frame). As notedpreviously, during encoding of P-frames in BIE, the encoder is forced toencode all blocks using intra modes. At block 834, a video input 832 isreceived for encoding. At block 836, a tiled encoder is configured forimplementing a BIE process as set forth above. For each frame of thevideo input, an iterative process may be implemented to effectuateappropriate coding decisions on a frame-by-frame basis, which commenceswith a determination as to whether the video sequence has reached itsend (block 838). If the end is not reached (i.e., there remain frames inthe video sequence requiring processing), a next frame is obtained(block 840). If the frame is determined to be a first frame of a GOPstructure (block 842), it is encoded as a regular I-frame (block 854)and the process flow returns to obtaining a next frame (block 840).Otherwise, it is encoded as a P-frame (block 844). For each slice of theP-frame, it is encoded or provided with a P-slice header (block 846).For each block or any other suitable coding unit of the P-slice, theencoder is configured to encode the image data in intra mode (block848). Thereafter, the process flow returns to determine whether all theframes have been processed (block 838). If so, the encoding of the videosequence is finalized (block 850), which may be provided as BIE-tiledbitstream to a downstream entity (e.g., a packaging system), as setforth at block 852. An alternative arrangement, B-frames may be used inlieu of P-frames for generating X-frames as noted elsewhere in thepatent application. Accordingly, blocks 844, 846 and may be suitablymodified to support this arrangement.

In a further embodiment of the present invention, X-frames may be usedonce in each GOP (instead of multiple times as in BIE) based on a PEscheme as noted previously. Essentially, PE-based tiled encodinginvolves a process and apparatus for generating a stream where all theframes have P-slice headers, except for the first frame which is anI-frame, while periodically there is an X-frame (i.e., BIE-frame orAIE-frame), where all blocks are intra-encoded but the slice headers areof P-slices (or B-slices where B-frames are also encoded in a sequence).In general, all slices of any two pictures that are to be potentiallyused as inputs to stitching need to have the same slice type, slice qp,as well as a number of other settings in the slice header and PPS. Incontrast with the BIE scheme set forth above, where all the frames of aGOP are X-frames except for the first one, an embodiment of a PE schemeis configured to provide X-frames only at select frame locationsdepending on two parameters: period (which is the size of the GOP, i.e.,the number of frames in the GOP) and phase (which is an integer in therange {0 to [period-1]}. Frame locations where the X-frames appear in aPE scheme may be determined as follows. Let N be the total number offrames in a stream. The first frame is encoded as an I-frame. For aframe at i^(th) position, it is encoded as a regular P-frame if {i Mod(period)≠phase}; and otherwise (that is, {i Mod (period)=phase}), theframe is encoded as an X-frame (with P-slice headers and all blocksencoded in intra-mode, independent of previous frames). It should benoted that an example PE scheme may provide as many phase-encodedstreams for each quality/bitrate representation of the media input asthere are frame locations in a GOP (i.e., GOP size).

By using P- or B-slice headers rather than I-slice headers in X-framesfor purposes of the present invention, several advantages may berealized in an exemplary embodiment, including but not limited tofacilitating mid-GOP switching in a user viewing environment. Assume theuser is watching a 360° immersive video program or content where thedirectly-gazed field of view (FoV) is in high quality (i.e., lower QP)and the user moves his head in the middle of the GOP. The user now seesa low quality video (higher QP) in their new field of view or viewport.The server can send an I-frame of a high quality (low QP) at thebeginning of the next GOP, but this introduces a significant latency, asit would take time until the high quality I-frame of the next GOP forthe viewport will be presented. It is desirable to receive or obtain anI-frame of the new field of view that is encoded at high quality as soonas possible while in the middle of the GOP. But it is not feasible tojust put an I-frame as is in the middle of the GOP in a conventionalimmersive video viewing environment. By generating an X-frame (i.e.,Block-Intra coded frame or All-Intra coded frame) and transmitting it inthe middle of the GOP (at any frame location in a GOP structure, forinstance), an embodiment of the present invention is thus effectivelyable to upgrade the quality of the field of view similar to the effectif an I-frame is presented in the middle of the GOP with high qualitytiles. By providing P-slice headers in AI- or BI-encoded frames (i.e.,AIE/BIE frames or X-frames), an embodiment of the present inventiontherefore allows a frame having high quality data in a region ofinterest (ROI) of FoV to be used in the middle of the GOP.

Further, in a tile encoding scheme where a frame is partitioned intotiles and slices, an embodiment of the present invention involvingX-frames enables mixing tiles in a single output compressed frame, wheresome tiles may use spatial or temporal prediction (i.e., inter-pictureprediction) and some tiles may use only spatial prediction (e.g.,comprising intra-coded blocks only). The tiles consisting of intra-codedblocks only may originate from an X-frame. In the context of the presentpatent application, the terms “mixing”, “muxing”, “stitching”,“splicing” or terms of similar import with respect to output streamgeneration may refer to means and methods to concatenate one compressedtile (e.g., tile A) with another compressed tile (e.g., tile B) to forma part of the bitstream representing a single output frame, where tile Aand tile B may originate from separate encodings of the content, whichwill be set forth in additional detail further below.

One of the advantages of a PE scheme relates to overcoming the issue ofdrift that may be present in a BIE scheme (i.e., drift elimination orreduction). It should be appreciated that while BIE allows replacement aP-frame of the previous viewport with an X-frame of the new viewport,the following frames are regular P-frames of the new viewport that areencoded with predictions made to previous frames. Thus, when a P-frameis replaced with an X-frame and then a following frame uses this X-framefor prediction instead of the original frames of the regular bitstream,there is a potential for drift where prediction errors may accumulate.On the other hand, in phased encoding, the generated stream uses theX-frame at position=<phase>+i*<period> for the prediction of thefollowing P-frames, and thus the situation where a P-frame uses forprediction a different frame than the frame used during encoding isavoided. Hence, there is no prediction error presented due to predictingfrom a frame that is different than the frame generated during theencoding, and accordingly, any potential drift due to this type ofprediction errors is avoided. However, the PE scheme may require alarger amount of storage since storage of the P-frames that follow theX-frames in the GOP is required.

Further, an embodiment of a PE scheme may be advantageously utilized tofacilitate gradual refreshing of frames whereby lower latency isachieved during playout by selecting only a subset of the tiles toupgrade their quality and send their appropriate phased-encoded tiles.While in an embodiment of a BIE scheme, a P-frame is replaced with anX-frame, in a gradual refresh frame annealing scheme the PE-codedstreams may be used to replace selected tiles with the correspondingtiles taken from the appropriate PE-coded stream. On the other hand, inanother embodiment, a BIE scheme may can also advantageously operate ona tile-by-tile basis. With respect to a PE-based embodiment,accordingly, if period is P and frame number is X, one can obtain thecorresponding phase by the following equation: Phase={X Mod P}. Thus,during delivery or playout of a coded video sequence, assume that acertain tile T is selected for upgrade to QP quality q in frame X, thenone can replace selected tile (in frame X and following frames until thenext upgrade/downgrade of T or viewport change) with the tile T from thestream with phase that satisfies the following relationship: Phase={XMod P} at QP=q. Thereafter, the co-located tiles in the frames followingframe X that belong to the same GOP are replaced by the correspondingco-located tiles from the same PE-encoded stream. It should beappreciated that the advantages of concatenating tiles from differentstreams when a user changes gaze direction are similar to the scenarioset forth above where the user changes his gaze during mid-GOP.Identical slice QPs are used for switching/replacing the tiles becauseif two input tiles are encoded with different actual QP and were encodedwith a single slice per picture, then if the slice QP differs, it wouldnot be possible for the QPs of tiles in the output stream to be correctwithout low-level rewrite of the stream. Additional details regardinggradual refresh frame annealing and tile selection will be set forthfurther below in reference to additional embodiments of the presentpatent application.

A potential disadvantage with respect to PE may be that it requires morestorage, since an input stream is encoded in many phases, potentiallyresulting in as many streams as the GOP size (rather than just twostreams as in BIE). This disadvantage may be traded off against theadvantage of reduced latency without drift in an example implementation.For fastest quality change response, the number of phases may be setequal to the size of the GOP, i.e., the period P, but an exampleembodiment may provide a trade-off of using fewer phases and consumingless storage while the latency of the quality upgrade may be longer,since tile upgrades will only be done on the next phase.

FIG. 9 is a flowchart illustrative of a PE scheme 900 according to anexample embodiment of the present invention. At block 902, a media inputstream corresponding to a 360° immersive video asset may be received. Asbefore, a plurality of bitrate representations of the media input streammay be generated, each bitrate representation having a separate videoquality, e.g., related to or controlled by a corresponding targeted QPvalue used for the bitrate representation and/or targeted bitrate, orother indicia of respective quality (block 904). Each bitraterepresentation controlled by a corresponding QP is encoded into aplurality of phase-encoded bitstreams, each phase-encoded bitstream thatbelongs to a particular bitrate representation comprising a number (N)of frames with a specific GOP structure having a GOP size (p), whereinthe number of the plurality of phase-encoded bitstreams equals the GOPsize. In one arrangement, the GOP size, i.e., p>1. For each p^(th)phase-encoded bitstream, N frames are encoded as follows: (i) at least afirst frame is encoded as an intra-coded (I) frame; and (ii) a frame ata frame position i, for 2≤i≤N, that satisfies the relationship {i Mod(GOP size)}=p is encoded as an X-frame having a slice header of aP-frame and comprising blocks of only intra-coded media image data only(i.e., similar to an I-frame). Otherwise, that frame is encoded as aregular P-frame having media data of a predictive-coded frame with aP-slice header (block 906). In some arrangement, the P-frames may alsocontain intra-coded data. Where B-frames are also encoded in anembodiment, an X-frame in lieu of a regular B-frame may be providedsimilar to the foregoing process. As noted previously with respect toFIGS. 5 and 7, operations set forth at blocks 904 and 906 may becombined to be executed in a single encode process for the sake ofcomputational efficiency in one example embodiment.

In an additional or alternative embodiment of a PE scheme, aphase-encoded bitstream may have a frame other than an I-frame as afirst frame of the coded video sequence, which may be achieved byappropriate settings in an encoder in accordance with the teachingsherein. For example, the first frame can be an X-frame (or some othernon-I frame). All other frames of the coded sequence may containpredicted frames (P/B-frames) and X-frames at suitable locations basedon phase.

FIG. 12 depicts a plurality of coded bitstreams 1200 having differentphases for a particular bitrate representation generated by a PE-basedtiled encoder system in an example embodiment. By way of illustration, aQP-N stream 1202-N having a QP value of 22 is encoded or otherwiseprovided as four phase-encoded streams 1204-1 to 1204-4 because of theuse of a GOP size of four frames in this example. For each PE stream1204-1 to 1204-4, the first frame is encoded as an !-frame 1206-1 to1206-4. The rest of the frames in each PE stream are encoded as eitherP- or X-frames based on the phase-position relationship set forth above.

Turning to FIG. 10A, depicted therein is a flowchart illustrative of aprocess 1000A for configuring a PE scheme in a tiled encodingarrangement according to an example embodiment of the present invention.At block 1002, an encoder may be initialized for selecting a PE schemewith respect to a media input stream corresponding to a 360° immersivevideo asset. At block 1008, period and phase parameters are obtained orotherwise configured, where period is equal to the GOP size (block 1004)and a phase is equal to or less than the GOP size (block 1006). At block1010, the encoder may be set to use tile encoding to generate tiles in aparticular grid/array arrangement per frame. Similar to a BIEconfiguration process set forth previously, a base_qp parameter may bewritten in slice QP headers of the encoded streams (block 1012). Atnoted before, it is required that all pictures with the same picturenumber to be used as an input for stitching must use the same base_qpvalue. Thus, it is not a necessary requirement in an example embodimentto set the same base_qp parameter in all the stream headers. Tofacilitate the encoded streams in different qualities (while having thesame base_qp), a qp_delta parameter may be configured as described abovewith respect to each stream based on target QPs (block 1014). As beforein an example BIE configuration process, a qp_delta of −10 may beconfigured where base_qp is 32 to achieve a target QP of 22 for aparticular stream. Spatial motion vector prediction may be configuredsuch that it is restricted within the tile only (block 1016). That is,motion vectors are not allowed to cross the tile boundaries in anexample embodiment (i.e., only intra-tile prediction is allowed and nointer prediction or context selection across a tile boundary isallowed). This means that motion vectors are set such that no sampleoutside the boundaries of any co-located tile is read during motioncompensation interpolation of the blocks inside a tile. An ROI grid maybe configured for the encoder such that it uses the qp_delta informationfor encoding a particular stream with respect to a specific region ofthe frames (block 1018). Further, TMVP may also be disabled (block 1020)in an example PE configuration process as noted above.

It should be noted that an example PE configuration process is roughlysimilar to a BIE configuration process in one embodiment, which may beperformed for every “phased” stream depending on the GOP size. Further,analogous to a BIE configuration process 800A that uses certainparameters, additional or alternative embodiments of a PE configurationprocess may involve other parameters in addition to and/or in lieu ofthe parameters exemplified in the flowchart of FIG. 10A.

FIG. 10B is a flowchart illustrative of blocks, steps and/or acts in anexample PE implementation according to an embodiment of the presentinvention. In general, an encoder may be configured to effectuateseveral decisions during PE-based tiled coding to generate an X-frameonly at specific frame locations of each phase-encoded stream. At block1034, a video input 1032 is received for encoding. At block 1040, atiled encoder is configured for implementing a PE process based on aperiod (block 1036) and phase (block 1038) as set forth above. For eachstream, the first frame is encoded as an I-frame (block 1042).Thereafter, an iterative process may be implemented to effectuateappropriate coding decisions on a frame-by-frame basis, which commenceswith a determination as to whether the video sequence has reached itsend (block 1044). If the end is not reached (i.e., there remain framesin the video sequence requiring processing), a frame index (i) isincremented (block 1046) and a next frame is obtained and denoted as ani^(th) frame (block 1048). A determination is made if the modularrelationship {i Mod (period)=phase} is satisfied. If so, the frame isencoded as an X-frame as set forth at blocks 1054, 1056 and 1058.Otherwise, it is encoded as a regular P-frame (block 1052). Thereafterthe process flow returns to determine if all the frames of the videostream have been processed (block 1044). If so, the process flowproceeds to finalize encoding the video stream (block 1060), which maybe provided as PE-tiled bitstream to a downstream entity (e.g., apackaging system), as set forth at block 1062.

As noted previously, a PE-based tiled encoding scheme facilitates agradual refresh annealing process during 360° video delivery, which willbe set forth in further detail below. An embodiment of phased encodingmay also be used during the playout where a stitcher executing on theserver side or on the client side may be used to combine tiles ofdifferent qualities. So, at every frame of the video being played, eachtile has a current quality, which may correspond to the QP value, targetbitrate or other indicia of the video stream the tile was taken from.When bandwidth is sufficiently large or when the user moves his head andthe viewport changes, it would be desirable to upgrade the quality(e.g., lower the QP) of some tiles (the tiles on the new viewport forexample). Furthermore, to reduce latency by means of reducing the usageof the buffer on the decoder side, an embodiment of the presentinvention provides that the entire viewport may not be upgraded at once,but rather upgrade it gradually by means of gradual refresh, onlyupgrading a few tiles in every frame, keeping the decoder buffer smalland thus reducing latency. As will be described in additional detailfurther below, an example bandwidth annealing apparatus may beconfigured to effectuate a process for determining which tile to upgradeat every moment based on the bandwidth, the viewport and/or currentbuffer utilization. Further, such a process may also be configured todetermine a quality level (i.e., which QP) to which a tile should beupgraded.

For example, assume that during playout, a tile selection apparatus(described in detail further below) determines to upgrade in the i^(th)frame, tile T to quality QP=q. This determination may be provided as acontrol input to a tile/frame stitcher module, which retrieves, receivesor otherwise obtains tile T from the i^(th) frame of the video streamthat was encoded with quality QP=base_qp+delta_qp=q using phasedencoding, where the phase is determined by the modular relationship:{phase=i Mod (period)}. Then, until the next time the tile selectionprocess decides to change the quality of this tile, tile T is taken fromthe same stream (i.e., the phased encoded stream with quality QP=q andwith the same phase). Accordingly, it will be appreciated that anadditional advantage of the PE scheme beyond the ability to perform agradual refresh of tiles during upgrades is better video quality.Overall, phased encoding gives a better QoE than a BIE scheme whereX-frames are substituted without phases, which can result in drift, andresult in lower peak signal-to-noise (PSNR) values, thereby resulting ina lower QoE stream for the remainder of the GOP. As noted previously, apotential drawback of phased encoding is the requirement of multiplestreams that can result in significant encode processing overhead andstorage space.

Example embodiments regarding how to stitch tile-encoded bitstreamsusing either PE or BIE schemes will be set forth below. As notedpreviously, tile-stitching embodiments may be implemented at a serverduring stream delivery phase or on the client side for playout. Ingeneral, example embodiments for stitching tiles involve utilizingbitstreams of different qualities (e.g., based on different QPs,targeted bitrates, or other indicia) as well as ensuring that there iscompatibility with respect to various pieces of parametric data relatingto video pictures, e.g., Video Parameter Set (VPS), Sequence ParameterSet (SPS), Picture Parameter Set (PPS), Supplemental EnhancementInformation (SEI), etc., among the bitstreams from which the tiles maybe selected. In general, the tile structure should preferably beconstant over time to facilitate stitching, which in turn is related totile-encoding processes performed by an encoder of the presentinvention. A bitstream stitcher module is operative in response to aninput comprising a list of tiles from different tile-encoded streams,which may be combined to generate a new output bitstream, where tilescloser to the viewport have a higher quality compared with tiles furtheraway from the viewport. Further, an example embodiment to perform thetile combination and stream muxing in accordance with the teachings ofthe present invention may be configured such that output streamgeneration still remains compliant within known codec standards such asMPEG HEVC/ITU-T/IS023008 part 2/H.265 specifications as well as emergingstandards such as AV1, H.266, VVC, and the like.

For stitching BIE-coded streams, tiles from the regular streams may beused by default for splicing (e.g., until some control input is providedbased on user's gaze or bandwidth allocation). The only instances wheretiles from the BIE-coded streams are taken is when either the viewportchanged (thereby requiring the X-frames which are frames with P-sliceheaders that can fit in the middle of the GOP but the tiles are intraencoded so the new viewport can be presented) or when a bandwidthannealing process determines to upgrade the quality of the tile (inwhich case the Block-Intra frame with the P-slice headers contains thetile with the upgraded higher quality).

FIG. 13A is illustrative of various blocks, steps and/or acts of anexample tile stitching scheme 1300A involving BIE-coded tiled streamsaccording to some example embodiments of the present invention. At block1302, a BIE bitstream stitcher receives input bitstreams of differentQPs, a first set comprising regular tile-coded streams and a second setcomprising BIE tile-coded streams. As noted above, the streams inexample embodiments are motion constrained and have the same base_qp foreach frame N as the base QP in any other frame N. A tile selectionmodule provides a list of tiles with different QPs (block 1306), whichforms part of overall input regarding the description and parametricinformation for each tile and the particular QP bitstream from which thetile is to be retrieved or obtained (block 1304). A tile stitchingprocess may be effectuated on a tile-by-tile basis, as set forth inblock 1308. If the viewport and/or the tile QP has/have changed (block1310), the tile is taken from a BIE-coded stream having the appropriateQP and stitched into the frame (block 1312). Otherwise, the tile istaken from a regular tile-encoded stream and stitched accordingly (block1314). After all the tiles are stitched in a frame (in a predeterminedgrid array), the stitched frame having different qualities of tiles maybe provided as output (block 1316). If additional video frames remainfor processing (e.g., encoding and stitching), the process flow maycontinue.

By way of illustration, consider a block-intra stream stitching scenarioin which there are at least three streams: (1) a regular stream of lowerquality (e.g. QP setting of 30); (2) a regular stream of higher quality(e.g. QP setting of 22); and (3) a BIE (all-Intra) stream of higherquality. Broadly, when the viewport changes, the quality of some tilesmay be increased. That is done in block 1312, which means that, e.g., atile at position A that in previous pictures was taken from stream (1)is now taken from stream (3). In the next picture, the tile at positionA should be taken from stream (2) if the tile is still within theviewport. If the tile is no longer within the viewport, the position Atile could be taken from stream (1). More particularly, it may befurther dependent upon gaze vector information. In other words, it isnot just if the tile at position A is in the viewport or not; rather, itis where the tile is located in a gaze-to-weight determination schemeused for tile selection (described in detail further below). Thus, itshould be understood that tiles within the viewport depending on wherethey are located may be upgraded or downgraded based on how far the tileare from the direct line of sight in an example embodiment of thepresent invention.

In similar fashion, an example tile stitching scheme 1300B involvingPE-based tiled streams is illustrated in FIG. 13B. A PE bitstreamstitcher is operative to receive input bitstreams of different QPs, eachencoded into a plurality of phase-encoded bitstreams (block 1332). Atile selection module provides a list of tiles with different QPs (block1336), which forms part of overall input regarding the description andparametric information for each tile and the particular QP bitstreamfrom which the tile is to be retrieved or obtained (block 1334). A tilestitching process similar to BIE tile stitching may be effectuated on atile-by-tile basis, as set forth in block 1338. If the viewport and/orthe tile QP has/have changed such that the quality of a current tile isrequired to change (block 1340), the tile is taken from a PE-codedstream having the appropriate QP based on a phase-frame modularrelationship and stitched into the frame (block 1342). For example, ifthe QP of tile at frame I changes to QP=q, the tile from the streamwhose phase equals {i Mod (period)} and QP=q is taken and stitched atappropriate location of a tile grid. Otherwise, the tile is taken fromthe same bitstream from which it was taken in the previous frame andstitched accordingly (block 1344). After all the tiles are stitched in aframe (in a predetermined grid array), the stitched frame havingdifferent qualities of tiles may be provided as output (block 1346).Further, if additional video frames remain for processing (e.g.,encoding and stitching), the process flow may continue.

Regardless of whether tiles from BIE-coded bitstreams or PE-codedbitstreams are stitched, an example embodiment of stitching may involvetaking tiles from different streams having compatible slice headers inaddition to other parametric information as set forth previously. Ingeneral, slice type (i.e., I/P/B-slice), the slice QP and other fieldsor parameters that may affect the CABAC decoding process may bemonitored to ensure compatibility and compliance. Further, someembodiments, such as example embodiments set forth in FIGS. 13A/13B, mayrequire that inter prediction is done using only the previously decodedpicture.

Turning to FIG. 13C, shown therein is a flowchart illustrative ofadditional blocks, steps and/or acts with respect to an example tilestitching/splicing scheme according to an example embodiment of thepresent invention. At block 1362, tiles of different QPs for the currentframe (to be stitched) are obtained as input. The data of the tiles(either from the BIE streams or from the PE streams) selected based on atile selection process is copied in a memory (block 1364). At block1366, the splicing process commences with a prototype slice header thatmay include a header field, an offset field, etc. (block 1368). For atile index (i), an entry_point_offset[i] may be determined from the tilesizes (block 1368). Bits needed for the largest value ofentry_point_offset[i] is determined (block 1370). The slice header maybe adjusted with a new Entry Point Offset (EPO) length based on thelargest offset value of all the tile indices as determined previously(block 1372). At block 1374, the EPO field is written into the sliceheader. Thereafter, the tiles are concatenated together after the sliceheader (block 1376), thereby generating an output bitstream of thestitched frame (block 1378).

Skilled artisans will recognize that in order to splice tiles they needto be retrieved from specific source bitstreams responsive to a tileselection process. To facilitate efficient retrieval, an embodiment ofsplicing may involve providing a memory-mapped tile pointer cache thatallows a quicker referencing of parsed files corresponding to tiles,wherein a file format is optimized to be memory mapped instead of beingparsed into RAM. Set forth below is an example file format for purposesof an exemplary splicing embodiment:

file format: u(16) magiclen; s(magiclen) magic_string; loop { // eachiteration is a group u(32) nrec; for (i=0; i<nrec; i++) { // per frameu(64) rec_end_relative[i]; } // rec_end_relative[i] is relative to theoffset of the file represented by this comment. // rec_end_abs[i] =this_offset + rec_end_relative[i] for (i=0; i<nrec; i++) { // thisiteration is per frame // prefixes are NAL units that appear before theSlice in the access unit u(32) n_prefixes; for (j=0; j<prefixes; j++) {u(64) prefix_start_abs[i][j]; u(64) prefix_len[i][j]; } // the sliceu(64) slice_start_abs[i]; u(64) slice_len[i]; u(32) n_tiles; for (j=0;j<n_tiles; j++) { u(64) tile_start_abs[i][j]; u(64) tile_len[i][j]; } //suffixes are NAL units that appear after the Slice in the access unitu(32) n_suffixes; for (j=0; j<n_suffixes; j++) { u(64)suffix_start_abs[i][j]; u(64) suffix_len[i][j]; } } } magic_string is“TPTCACHE1 [ii[ ][il[ ]llil[ ]il[ ]]]”

Referring to FIG. 14, shown therein is an example 360° video frame 1400comprising tiles selected and spliced from coded bitstreams havingdifferent qualities or QPs in accordance with an embodiment of thepresent invention. By way of illustration, video frame 1400 is formedfrom 128 tiles (16 columns by 8 rows) of a 4K video input, shown inunwrapped format (i.e., not projected in a 3D spherical space), whereina field 1402 which may correspond to an ROI of the frame 1400 based onthe viewport or gaze vector location. In accordance with the teachingsherein, ROI 1402 may be formed from splicing high quality tiles (i.e.,tiles selected from coded bitstreams having low QPs, e.g., QP-16 at105.6 Mbps, and concatenated in a stitching process). Regions or fieldsdisposed proximate/adjacent to ROI 1402 may have medium quality tiles(e.g., field 1404). On the other hand, fields or regions distallydisposed from ROI 1402, e.g., those farther away from the viewport, maybe formed from lower quality tiles, as exemplified by regions 1406 and1408.

To facilitate gaze-based tile selection control, additional embodimentsof the present invention involve monitoring where a user is viewing in a360° immersive video program (i.e., the user's viewport) and determiningappropriate tile weights based on the user's gaze. In general, a gazevector (GV) may be returned by the user/client device defining a gazedirection in a 3D immersive space displaying 360° video, e.g., where theheadset is pointed. In further embodiments, the user's eyeball movementmay be tracked for similar purposes. As will be seen below, the tiles ofa tiled frame also have direction vectors (which are not dependent onthe user's gaze) based on how the frame is mapped in a 3D displayenvironment. A dot product (also referred to as a scalar product orinner product) of tile vector and gaze vector can be calculated todetermine the angular separation between the gaze direction and thedirection of the middle of any tile of a frame, which may be provided toa weighting function module for determining corresponding tile weights.

FIGS. 15A and 15B are flowcharts illustrative of various blocks, stepsand/or acts of a gaze control scheme that may be (re)combined in one ormore arrangements, with or without blocks, steps and/or acts ofadditional flowcharts of the present disclosure, for facilitatingoptimized tile selection according to one or more embodiments of thepresent invention. Process 1500A involves receiving a gaze vector from aclient device operating to display a 360° immersive video asset to auser, wherein each video frame comprises an array of tiles projected ona 3-dimensional (3D) display environment viewed by the user in which theuser is immersed, the gaze vector defining a gaze direction in the 3Ddisplay environment where the user is viewing at any particular time(block 1502). In one embodiment, gaze vector information may comprise(x,y,z) information in a 3D Cartesian coordinate system that may beassociated with the display environment. In another embodiment, gazevector information may comprise (ρ,θ,φ) information in a 3D sphericalcoordinate system based on an equirectangular projection mapping. Inanother embodiment, a 3D gaze vector may be normalized (to obtain aunit-length directional vector). Skilled artisans will thereforerecognize that GV information may be provided in a number of waysdepending on geometrical modeling, projection mapping, computationalmethodology, etc., used in a particular implementation. At block 1504, adetermination may be made as to what the angular separation is betweenthe gaze vector and a directional vector associated with each tilelocation respectively corresponding to the array of tiles in the 3Ddisplay environment, which again may be dependent on the particulargeometrical modeling, projection mapping, computational methodology, andthe like. At block 1506, responsive to the angular separations, aplurality of tile weights are determined corresponding to the array oftiles for use in selecting tiles of different bitrate qualities (QPs) ofthe 360° immersive video asset for assembling a video frame to bedelivered to the client device. In general, tiles (or, more broadly,tile positions or locations) close to or within an arbitrary angulardistance from the gaze vector may be assigned higher values, whereastiles that are directly opposite to the gaze vector (i.e., 180° or πradians) may be assigned lowest weight values, with the remaining tilesin between (in both horizontal and vertical directions) receivingvarying weight values between the maximum and minimum values accordingto any suitable mathematical relationship (e.g., linear, quadratic,etc.).

Process 1500B sets forth additional details with respect to effectuatinggaze-based control in an example embodiment. At block 1522, tile weightsmay be determined as a function of a cosine of an angular separationbetween the gaze vector and the directional vector corresponding to atile location in a suitable 3D spatial projection of a 2D video frame ofthe 360° immersive video asset. At block 1524, the tile weights may beprovided as an input along with a dynamic bandwidth allocation input toa tile selection and bandwidth annealing process, which is furtherdescribed elsewhere in the present patent application.

In one example embodiment, depending on where the tile is located inrelation to the gaze vector, a determination is made how much bandwidthis allocated to that tile location corresponding to the weight. Wherethe gaze vector {right arrow over (a)} and tile directional vector{right arrow over (b)} are denoted by vectors, their dot product may bedetermined as follows:{right arrow over (a)}·{right arrow over (b)}=|a|·|b|cos θ

Upon normalization, i.e., if [â]=gaze/|gaze|, then |a|=1. Likewise, byassigning [{right arrow over (b)}]=tile_direction/|tile_direction|,|b|=1. Accordingly, by normalizing, the foregoing relationshipsimplifies to:â·{right arrow over (b)}=cos θ

Rather than mapping cos(θ) back to θ to determine a weight, anembodiment of the present invention involves defining a mathematicalfunction to map from cos(θ) to a weight as follows: x=cos(θ), andf(x)={x+1} if x>0 and f(x)=[α{x+1}] if x<0, where α=a scaling factor,e.g., 0.1. Thus, if the angular separation between a gaze vector andtile directional vector is 0°, cos(θ)=1 and f(x)=2. Likewise, for a tilethat is 60° or 300° away from the gaze vector, cos(θ)=0.5 and thecorresponding f(x) value is 1.5. In an equirectangular projection of a3D frame, the angle exactly opposite to where the user is looking is180°, which yields cos(θ)=−1.0, thereby obtaining a weight f(x) value of0 regardless of the scaling factor. Accordingly, an example embodimentmay provide a suitable scaling factor based on how smoothly or quicklytile qualities may vary in relation to a gaze direction within a frame.

FIG. 16A illustrates an example unit-circular geometrical arrangement1600A for facilitating determination of angular separation between auser's gaze direction and tile positions. A user location 1602 is set asthe center of a unit-circular cross section of a 3D spherical space. Byreferencing the user's gaze along a first referential axis (e.g.,X-axis) 1604, different angular displacements for the tile locations maybe determined as set forth above. By way of illustration, referencenumerals 1606 and 1608 refer to two tile directional vectors that are30° and 60° away from the gaze direction 1604. In general, tilelocations approaching near ±90° or thereabouts (e.g., reference numerals1610A/1610B) with respect to the gaze direction 1604 connote a user'smid-to-far peripheral vision and a weighted scaling factor may beutilized such that tiles in such regions and beyond may be allocated afaster reduction in bandwidth (i.e., lesser quality). At a directionalvector location 1614, the tiles are ±180° away from the gaze direction1604.

In an example embodiment, instead of actual angular displacements,cosine values corresponding to different locations may be provided inreference to the gaze direction. For instance, if a tile directionvector is 90° or 270° from the gaze vector, x=0.0 may be fed to theweighting function, which yields a weight of 1.0. Likewise, for a tiledirection vector is 330° away, x=0.866 is provided to the weightingfunction, thereby yielding a weight value of 1.866. As a furtherexample, if the tile direction vector is 120° deg away, x=−0.5, isprovided to the weighting function, thereby yielding a weight value of0.05 (assuming α=0.1), which is the same if the tile direction were 240°away from the gaze vector).

Further, both gaze vector information and tile direction vectorinformation may be converted to appropriate tile coordinate informationrelative to the tile grid used in tile encoding during media preparationfor facilitating identification of tiles by rows and columns, which maybe input along with the weight information to a tile selection andbandwidth annealing process. One skilled in the art will recognize thatthe determination of tile coordinate information is dependent on theprojection mapping used in an example embodiment. FIG. 16B illustratesan equirectangular projection mapping scheme resulting in a sphericaldisplay environment 1600B where the tiles form the surface. One exampleimplementation provides placing a north pole 1605 in the direction of{0,1,0} and a south pole 1607 in the opposite direction, whereas theleft and right edges of a tiled frame are in the direction of {0,0,1}and the center of the image (i.e., the tiled frame) is in the directionof [0,0,−1}. In an example implementation involving uniform tile sizes,an embodiment of the present invention provides an apparatus and methodfor determining the location of a tile 1609 which has a directionalvector 1611, which may be configured to compute t_(x) (the column indexof the tile) and t_(y) (the row index of the tile) for a given gridarrangement of n_(x) (the number of tile columns) and n_(y) (the numberof tile rows) as follows, where θ is the polar angle and φ is theazimuthal angle of the spherical coordinate system:θ={[t _(x)+1/2]/n _(x)}2πφ=└1/2−{t _(y)+1/2}/n _(y)|πy=sin φr=cos φz=r*cos θx=r*sin θ

Where the encoding has non-uniform tile sizes, the foregoing equationsmay be modified based on, e.g., pixel areas of individual tiles, etc. Byway of illustration, using (i) as the tile index for the left edge oftile column i, (j) as the tile index for the top edge of the tile row j,w is the number of pixel columns, and h is the number of pixel rows, anembodiment of the present invention may be configured to determine thefollowing wherein both x_(i) and y_(j) involve a “floor” operator toround out (i.e., the fractional part is removed) with respect to usingan example coding unit or block size (e.g., 64 pixels):

$x_{i} = {\left\lfloor \frac{iw}{64n_{x}} \right\rfloor 64}$$\theta = {\frac{x_{i} + x_{i + 1}}{2w}2\pi}$$y_{j} = {\left\lfloor \frac{jh}{64n_{y}} \right\rfloor 64}$$\phi = {\frac{y_{j} + y_{j + 1}}{2h}2\pi}$

FIG. 16C is illustrative of an example 360° immersive video viewingenvironment 1600C for purposes of one or more embodiments of the presentinvention. A premises node or gateway (GW) 1642 associated withsubscriber premises 1640 is served by a delivery pipe 1644 for providingimmersive media content. In one arrangement, such immersive mediacontent may be presented in a 3D-panoramic virtual space viewed in asuitable headset worn by the subscriber/user. An example UE may comprisea CPE 1646 served by GW 1642, such as a gaming console, laptop, or asmartphone, for example, that executes one or more gaming or mediaapplications to provide suitable signals to one or more devices such asa display device 1636 mounted to or on a user's head 1628. Additionalexamples of such devices may comprise visors, goggles, wired/wirelessheadgear or helmets, masks, etc. that can display or effectuate animmersive viewing space surrounding the user. In an example displaydevice arrangement, there may be additional instrumentation such as agyroscope, accelerometer and a magnetometer, etc., to facilitate headtracking, i.e., when the user 1628 moves her head, the field of viewaround the simulated space may move accordingly, along with a portion ofthe space being gazed at (i.e., the viewport) by the user. Thus, in ahead-tracking headset, the cone of view or field of view as well as theuser's viewport moves around as the user looks up, down and moves sideto side or angles her head. An example system may include the so-called6DoF (six degrees of freedom) arrangement that can plot the user's headin terms of X-, Y- and Z-axes to measure head movements, also known aspitch, yaw and roll, which may be used for tracking the user's point ofview within the simulated 3D panoramic viewing space.

By way of illustration, CPE 1646 may be embodied as a platform 1648including one or more processors 1656, volatile andnonvolatile/persistent memory 1654, input/output (I/O) interfaces 1660(e.g., touch screens, gaming controllers, hand-tracking gloves, etc.),as well as one or more 360-degree media/gaming applications 1638 thatcan effectuate a 3D virtual viewing space or “screen” 1620 for the user1628 wearing head-mounted display (HMD) 1636. In one examplearrangement, HMD 1636 may be wirelessly coupled to CPE 1646 via wirelessinterface 1642. A plurality of decoder buffers 1645 may be provided aspart of an example CPE platform 1646/1648 corresponding to one or more360° immersive video content channels available to the user 1628.

Additional 3D-media-capable CPE 1634 (e.g., a tablet, phablet orsmartphone, etc.) may also be separately or optionally provided. ExampleCPE apparatus 1646/1634 operating together or separately in conjunctionwith HMD 1636 may be operative to effectuate 3D virtual viewing space1620 that is an immersive environment in which the user 1628 can moveher point of view in full 360° in one of a vertical plane, a horizontalplane, or both planes, defined in the 3D environment, wherein theviewport 1624 changes accordingly. In an additional or alternativearrangement, CPE apparatus 1646/1634 operating in conjunction with HMD1636 may be operative to effectuate a 3D virtual viewing space 1620 thatmay be partially immersive in that it is less than 360° along any one ofthe axes.

A movement and gaze detection module 1662 is operative to detect amovement in a point of view or gaze direction of the user/subscriber1628 with respect to the 3D virtual viewing space 1620 and provide asuitable gaze vector output to a serving node as the subscriber 1628shifts her gaze within the viewing space 1620. In one embodiment, a tileweighting module may be configured to operate at a 360° videooptimization node (e.g., node 216 in FIG. 2) to determine appropriatetile weights based on the gaze vector information. In anotherembodiment, tile weighting may be performed locally at example apparatus1646/1634 and/or at HMD 1636.

FIG. 17A is a flowchart illustrative of additional blocks, steps and/oracts with respect to an example 360° immersive video optimizationprocess according to an example embodiment of the present invention. Inparticular, process 1700A exemplifies client-side processing withrespect to gaze/movement detection in one implementation. At block 1702,a user commences a 360° video session, whereupon a client device sends arequest to a back office node (e.g., node 238 in FIG. 2) with respect toa requested 360° video asset (block 1704). At block 1706, the backoffice node responds with a URL for the requested asset and provides avideo session ID to the client. Responsive thereto, the client devicecommences receiving the encoded video asset via streaming from thelocation identified in the URL, which a device player of the clientdevice decodes and renders in a 3D immersive environment (block 1710).Also, the client device may commence monitoring or tracking head/ocularmovement of the user operating the client device in connection with theongoing 360° video session (block 1708). Responsive to detecting that amovement is detected (block 1712), gaze vector information with respectto a current viewport is provided to a 360° video optimization node(e.g., node 216 in FIG. 2), which utilizes the gaze vector informationin combination with other pieces of information in a bandwidth annealingand tile selection process (block 1714). In one embodiment, gaze vectorinformation may be generated until the user has stopped playing thevideo and/or no head/ocular movement is detected (e.g., over a period oftime), as illustrated in an iterative loop involving decision blocks1712 and 1716. In one embodiment, gaze vectors may be generated at apredetermined frequency (e.g., 40 times per second). As will be seenbelow, not all gaze vectors may be utilized in an example bandwidthannealing and tile selection process, which may be configured to betriggered only when there is a need for tile quality modification, e.g.,upgrading or downgrading. When the user stops playing the video asset,appropriate session termination request/message may be generated to thedelivery sever (block 1718), whereupon the process flow may terminate(block 1720).

Set forth below is a list of gaze vectors provided by a client device inan example implementation over a configurable time window:

0.3203731, 0.1810199, 0.9298348 0.3201844, 0.1811305, 0.92987840.3201652, 0.1811581, 0.9298795 0.3201838, 0.1811286, 0.92987890.3201413, 0.1811444, 0.9298905 −0.02325181, −0.6079658, 0.7936227−0.01977778, −0.6028962, 0.7975745 −0.01794935, −0.6024268, 0.7979723−0.01342396, −0.6015137, 0.7987497 −0.01229509, −0.6009697, 0.7991772−0.0120346, −0.5997405, 0.8001041 −0.01373066, −0.6005607, 0.7994613−0.01506477, −0.5993657, 0.8003336 −0.01094525, −0.5975212, 0.8017784−0.009084027, −0.5964078, 0.8026301 −0.008858532, −0.5953203, 0.8034396−0.00746176, −0.5926894, 0.8053966 −0.007450074, −0.5930958, 0.8050975−0.01072073, −0.5926897, 0.8053595 −0.01269324, −0.5921446, 0.8057318−0.01323339, −0.5883871, 0.8084711 −0.01338883, −0.586729, 0.8096727−0.01282388, −0.5847392, 0.81112 −0.01634659, −0.5839438, 0.8116295−0.02636183, −0.5821166, 0.8126778 −0.02774585, −0.5801842, 0.8140126−0.0245801, −0.5784537, 0.8153448 −0.02183155, −0.5797198, 0.8145235−0.02022467, −0.5769228, 0.8165482 −0.9961338, 0.007874234, 0.0874956−0.9719607, −0.02848928, 0.2334113 −0.9855442, −0.0176625, 0.1684957−0.9825167, −0.0296559, 0.1837972 −0.9824995, −0.03729712, 0.182493−0.982159, −0.03973407, 0.1838061 −0.9689301, −0.02837855, 0.2457015−0.8717358, −0.01528142, 0.4897378 −0.4374043, −0.01084228, 0.89919960.2052692, 0.0161775, 0.9785718 0.6165089, −0.005071477, 0.78733160.7826833, −0.01918624, 0.6221244 0.778906, −0.0795427, 0.62207590.7230754, −0.0673095, 0.6874819 0.6768191, −0.06240646, 0.73349940.5633906, −0.0747445, 0.8228027

In a non-normalized format, example GVs in a Cartesian coordinate systemmay comprise (x,y,z) values such as [3,5,1]; [10,4,1], etc. In anormalized spherical coordinate system, the GV values may comprise setsof angles such as, e.g., (59.04°,80.27°), where r=radius has beennormalized out, 8=polar inclination and φ=azimuth angle. Regardless ofthe format, whereas the gaze vector information may be provided orotherwise obtained at configurable frequencies, time periods, etc., notall gaze vectors may need to be utilized in a tile weight determinationprocess. For example, tile weights may be determined and utilized onlyin response to triggering a tile selection and bandwidth annealingprocess, as noted previously with respect to certain embodiments.Accordingly, unused gaze vector information may be periodicallydiscarded in such embodiments.

FIG. 17B is a flowchart illustrative of additional blocks, steps and/oracts with respect to further aspects of an example 360° immersive videooptimization process according to an example embodiment of the presentinvention. In particular, process 1700B illustrates server-sideprocessing with respect to tile weight determination based ongaze/movement detection and utilization of tile weights in bandwidthannealing and tile selection, inter alia, in an example implementation.At block 1742, a video back office node receives a user request forcommencing a session, whereupon a session setup request may be generatedto a 360° video optimization system (block 1744). Responsive toobtaining appropriate pieces of information, e.g., session ID, session'smanifest URL, etc., the back office provides the requisite informationto a client device for starting the requested video asset (block 1746).A bandwidth annealing and QoE management module with tile selectionfunctionality (also referred to as BWA-TS module in some embodiments) isoperative to obtain, retrieve, read and/or process the manifestassociated with the requested video asset in all encodingrepresentations (block 1748). At block 1750, BWA-TS module may also beconfigured to receive dynamic bandwidth notifications from the deliverynetwork infrastructure (e.g., DSLAM/CMTS in an example embodiment) withrespect to the client device's video session. At block 1752, BWA-TSmodule is operative to extract specific tiles from the tiled encodingstreams or representations. At block 1754, BWA-TS module is operative toreceive control inputs (blocks 1756, 1758) regarding bandwidthallocation for the 360° immersive video session as well as any gazevector information. As noted previously, if the gaze vector input is notavailable initially, a default value may be used that may beconfigurable based on content type, content provider policy, clientdevice type and capabilities, etc. Responsive to the control inputs,BWA-TS functionality is operative to generate or otherwise indicate aselected set of tiles based on the bandwidth and tile weights (block1754). A tile combining/stitching and stream generation functionality(also referred to as TC-SG module in some embodiments) is operative toreceive the selected tile set (block 1760), which may be concatenated asset forth hereinabove. Accordingly, in one implementation, a video sliceheader is concatenated with select tiles and appropriately modified toinclude applicable entry point offsets (block 1762). For purposes oftile stitching, certain operations may be performed at a NetworkAbstraction Layer (NAL) access unit level, where the coded video data isorganized into multiple NAL units in a tiling hierarchy. A NAL accessunit, which is effectively a packet that contains an integer number ofbytes, may be treated as a logical substructure of an elementary streamformed by binary audio/video flows and compressed to facilitatebitstream manipulation access. In one implementation, it is the smallestdata organization that is possible to be attributed in a system ofsynchronization involving layer compression, where MPEG decodingoperations may be made, taking into account that consistency among thevideo parametric information (e.g., spatial/temporal redundancy, etc.)is maintained.

Continuing to refer to FIG. 17B, at block 1764, TC-SG module is providedwith a segment of data for one frame/picture comprising combined tiles,which may be containerized in a suitable container format, e.g., MPEG-2Transport Stream container format (M2TS; also referred to as MP2TSsometimes), MPEG 4 part 14 (MP4) container format, or ISO Base MediaFile Format (ISOBMFF) container format, and the like (block 1766). Adelivery server may be configured to deliver the muxed picture/frame tothe client device over a suitable network (block 1768). As set forth inthe embodiment of FIG. 17B, operations comprising BWA-TS, TC-SG anddelivery service of process 1700B may continue to take place until thedelivery communications socket is closed or timed out (block 1770).Thereafter, the 360° video session with the client device may beterminated (block 1772).

In an example embodiment, the bandwidth allocation for an exemplary 360°immersive video session may be 19 Mb/s. The video may be encoded withfull 360 video using a 128-tile grid, covering bitrates varying from ahigh of 105.6 Mb/s with a QP value of 16 to a low of 7 Mb/s with a QPvalue of 30. The higher quality tiles are targeted at the user's directfield of vision. The quality of tiles degrades (i.e., QP values rise) inproportion to the distance from the user's direct field of vision. Thefunctionality of BWA-TS insures that the overall bandwidth of the 360video session is not exceeded. The tile selection is based on thebitrate of each tile. In an example when the user is looking up at acloudy sky in a scene, most of the tiles provided in that viewport arerelatively high quality. The content of the tiles when looking up insuch a scenario is relatively static (i.e., very little motion) andtherefore not as many bits are dedicated to the low motion areas by theencoder. This results in the ability to show tiles from the highestquality video encoding with a QP value of 16. When the bandwidthallocation for the 360 video is reduced (for example from 19 Mb/s to 7Mb/s), the quality of the tiles is also reduced. In the foregoingexample, the highest quality tiles in the direct field of vision mayhave a bitrate of 22.4 Mb/s with a QP value of 22.

FIG. 18A illustrates a tile-weighted frame 1800A comprising 16-by-8array of tiles, wherein each tile is assigned a weight based a gazevector of {0.783, 0.396, −0.481} provided by a client device in anexample implementation. Reference numeral 1802 refers to a viewportassociated with the gaze, where the tiles are given highest values inaccordance with the teachings of the present invention. One skilled inthe art will recognize that as the viewport changes, the region of tileswith highest values also changes concomitantly. In a 360° immersivevideo display space based on equirectangular projection, the region oftiles with highest values thus also moves around, e.g., to the polarregions if the user is gazing directly up or down, or to the equator ifthe user is gazing directly in the middle of a picture. By way ofillustration, FIG. 18C depicts a 3D immersive display or viewing space1800C where the tiles of highest quality are near the North Pole region1852 when the user is directly looking up, with the progressively lowerquality tiles forming the remaining portion of the immersive space,wherein the lowest quality tiles are located near the South Pole region1854. Likewise, FIG. 18D depicts a 3D immersive display or viewing space1800D where the tiles of higher quality are near the South Pole region1854 when the user is directly looking down, with the progressivelylower quality tiles spanning toward the North Pole 1852.

FIG. 18B illustrates a device frame buffer 1800B in an exampleembodiment. Three consecutive frames 1822A-1822C in the buffer areillustrated, each having a P-slice header but comprising different setsof tiles in a viewport 1820 based on the headset view. Whereas a currentframe 1822A has all I-tiles in its viewport 1820, the following framesare shown with viewports 1820 having P-tiles.

As noted hereinabove, an aspect of the functionality of a BWA-TS moduleis to insure that the overall bandwidth of an example 360° immersivevideo session does not exceed a designated bandwidth allocation (e.g.,based on network operator policies, content provider policies,subscriber/device policies, or any combination thereof), while stillmaximizing quality and viewing experience. Optimized tile selectionhaving suitable bitrate qualities may therefore be configured responsiveto a user's field of vision, bandwidth allocation/limitation, bitratesper tile as well as a transmit buffer model such that tiles in thedirect line of sight have the best quality possible, with decreasingqualities moving farther away from the direct gaze.

FIG. 19 is a flowchart illustrative of various blocks, steps and/or actsof a BWA-TS process 1900 that may be (re)combined in one or morearrangements, with or without blocks, steps and/or acts of additionalflowcharts of the present disclosure, according to one or moreembodiments of the present invention. As set forth at block 1902,process 1900 may commence with or responsive to receiving, retrieving orotherwise obtaining one or more stream manifest files provided by a 360°video asset packager (e.g., packager 214 in FIG. 2) with respect to aplurality of tile-encoded streams that may be generated according to aBIE or PE scheme. In general, the manifest files may include informationor data describing various characteristics of tile groupings per frame,including location URLs, bitrates, slice/block type, media type, etc.,for each tile-encoded bitstream corresponding to a particular one of aplurality of bitrate representations of a media input stream. In onearrangement, manifests may be organized in a hierarchical manner, i.e.,with certain manifests for describing overall coded bitstreams, whileother manifests are provided for describing individual tiles in astream. As set forth passim in the present patent application, eachstream is a particular bitrate representation of the source media havinga video quality, e.g., related to or controlled by a corresponding QPused for the bitrate representation, and/or targeted bitrate, or otherindicia, wherein each frame of a tile-encoded bitstream comprises anarray of tiles organized into at least one slice per frame, wherein aplurality of frames form a GOP structure of the tile-encoded bitstream.At block 1904, process 1900 proceeds to receiving, retrieve or otherwiseobtain gaze vector information, and responsive thereto, determines tileweights corresponding to an array of tiles forming a frame, e.g., basedon the gaze vector or by default settings. At block 1906, process 1900proceeds to receive, retrieve or otherwise obtain variant weightscorresponding to the plurality of bitrate representations or associatedtile-encoded bitstreams of the media input stream. In one arrangement,the variant weights may be defined as a policy-based property of thestreams where higher quality stream representations (i.e., variants) areaccorded a higher priority or weight that may be used in furthercomputations involving weight based knapsack packing selections. Atblock 1908, a determination is made with respect to an adequacy metricvalue as a function of a variant weight and a tile weight for eachtile/GOP-tuple combination over a set of frames across a GOP structurefor each of the tile-encoded bitstreams. At block 1910, process 1900proceeds to selecting tiles having different bitrate qualities fromcorresponding tile-encoded bitstreams for assembling a frame, responsiveat least in part to the adequacy metric values, wherein the bitratequalities of the selected tiles are optimized to satisfy a transmitbuffer model for transmitting a multiplexed video output stream.Thereafter, a list of the selected tiles may be provided to a tilestitcher for generating a frame containing the selected tiles as part ofthe muxed video output stream (block 1912). Where the tile stitching isperformed in a device-side embodiment, the selected tiles may beprovided to the client device in an example embodiment, as notedelsewhere in the present patent application.

An example stream-level manifest for purposes of an embodiment of thepresent invention is illustrated below:

<?xml version=“1.0”?> <TiledMediaDefinition> <TileGroup> <Representation tiles=“128” columns=“16” rows=“8” height=“2160” id=“1”mimeType=“video/H265” width=“3840” QP=“16”><URL>race360-105Mbs.hevc</URL>  </Representation>  <Representationtiles=“128” columns=“16” rows=“8” height=“2160” id=“2”mimeType=“video/H265” width=“3840” QP=“18”><URL>race360-64_6Mbs.hevc</URL>  </Representation>  <Representationtiles=“128” columns=“16” rows=“8” height=“2160” id=“3”mimeType=“video/H265” width=“3840” QP=“20”><URL>race360-39Mbs.hevc</URL>  </Representation>  <Representationtiles=“128” columns=“16” rows=“8” height=“2160” id=“4”mimeType=“video/H265” width=“3840” QP=“22”><URL>race360-24_4Mbs.hevc</URL>  </Representation>  <Representationtiles=“128” columns=“16” rows=“8” height=“2160” id=“5”mimeType=“video/H265” width=“3840” QP=“24”><URL>race360-16_2Mbs.hevc</URL>  </Representation>  <Representationtiles=“128” columns=“16” rows=“8” height=“2160” id=“6”mimeType=“video/H265” width=“3840” QP=“26”><URL>race360-11_4Mbs.hevc</URL>  </Representation>  <Representationtiles=“128” columns=“16” rows=“8” height=“2160” id=“7”mimeType=“video/H265” width=“3840” QP=“28”><URL>race360-8_6Mbs.hevc</URL>  </Representation>  <Representationtiles=“128” columns=“16” rows=“8” height=“2160” id=“8”mimeType=“video/H265” width=“3840” QP=“30”> <URL>race360-7Mbs.hevc</URL> </Representation> </TileGroup> </TiledMediaDefinition>

An example lower-level manifest based on DASH-MPD for purposes of anembodiment of the present invention involving multiple phase encodedstreams is illustrated below:

<?xml version=“1.0” encoding=“UTF-8” ?> - <MPDxmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance”xmlns=“urn:mpeg:dash:schema:mpd:2011”xsi:schemaLocation=“urn:mpeg:dash:schema:mpd:2011 DASH- MPD.xsd”type=“static” mediaPresentationDuration=“PT654S” minBufferTime=“PT2S”profiles=“urn:mpeg:dash:profile:isoff-on- demand:2011”>  - <Periodtag=“batman-plain”> - <AdaptationSet mimeType=“audio/mpegts”>  -<Representation> <BaseURL>batman-audio.ts</BaseURL>   </Representation> </AdaptationSet> - <AdaptationSet mimeType=“video/mp4”framePeriod=“1/24”>  - <Representation label=“batman qp 16 @ 38.0”weight=“37.99” graphNote=“16”> <BaseURL phase=“0” label=“batman phase 0qp 16”>batman-phase-0-qp16.mp4</BaseURL> <BaseURL phase=“1”label=“batman phase 1 qp 16”>batman-phase-1-qp16.mp4</BaseURL> <BaseURLphase=“2” label=“batman phase 2 qp 16”>batman-phase-2-qp16.mp4</BaseURL><BaseURL phase=“3” label=“batman phase 3 qp16”>batman-phase-3-qp16.mp4</BaseURL> <BaseURL phase=“4” label=“batmanphase 4 qp 16”>batman-phase-4-qp16.mp4</BaseURL> <BaseURL phase=“5”label=“batman phase 5 qp 16”>batman-phase-5-qp16.mp4</BaseURL> <BaseURLphase=“6” label=“batman phase 6 qp 16”>batman-phase-6-qp16.mp4</BaseURL><BaseURL phase=“7” label=“batman phase 7 qp16”>batman-phase-7-qp16.mp4</BaseURL> <BaseURL phase=“8” label=“batmanphase 8 qp 16”>batman-phase-8-qp16.mp4</BaseURL> <BaseURL phase=“9”label=“batman phase 9 qp 16”>batman-phase-9-qp16.mp4</BaseURL> <BaseURLphase=“10” label=“batman phase 10 qp16”>batman-phase-10-qp16.mp4</BaseURL> <BaseURL phase=“11” label=“batmanphase 11 qp 16”>batman-phase-11-qp16.mp4</BaseURL> <BaseURL phase=“12”label=“batman phase 12 qp 16”>batman-phase-12-qp16.mp4</BaseURL><BaseURL phase=“13” label=“batman phase 13 qp16”>batman-phase-13-qp16.mp4</BaseURL> <BaseURL phase=“14” label=“batmanphase 14 qp 16”>batman-phase-14-qp16.mp4</BaseURL>   </Representation> _(—)  <Representation label=“batman qp 18 @ 28.9” weight=“28.88”graphNote=“18”> <BaseURL phase=“0” label=“batman phase 0 qp18”>batman-phase-0-qp18.mp4</BaseURL> <BaseURL phase=“1” label=“batmanphase 1 qp 18”>batman-phase-1-qp18.mp4</BaseURL> <BaseURL phase=“2”label=“batman phase 2 qp 18”>batman-phase-2-qp18.mp4</BaseURL> <BaseURLphase=“3” label=“batman phase 3 qp 18”>batman-phase-3-qp18.mp4</BaseURL><BaseURL phase=“4” label=“batman phase 4 qp18”>batman-phase-4-qp18.mp4</BaseURL> <BaseURL phase=“5” label=“batmanphase 5 qp 18”>batman-phase-5-qp18.mp4</BaseURL> <BaseURL phase=“6”label=“batman phase 6 qp 18”>batman-phase-6-qp18.mp4</BaseURL> <BaseURLphase=“7” label=“batman phase 7 qp 18”>batman-phase-7-qp18.mp4</BaseURL><BaseURL phase=“8” label=“batman phase 8 qp18”>batman-phase-8-qp18.mp4</BaseURL> <BaseURL phase=“9” label=“batmanphase 9 qp 18”>batman-phase-9-qp18.mp4</BaseURL> <BaseURL phase=“10”label=“batman phase 10 qp 18”>batman-phase-10-qp18.mp4</BaseURL><BaseURL phase=“11” label=“batman phase 11 qp18”>batman-phase-11-qp18.mp4</BaseURL> <BaseURL phase=“12” label=“batmanphase 12 qp 18”>batman-phase-12-qp18.mp4</BaseURL> <BaseURL phase=“13”label=“batman phase 13 qp 18”>batman-phase-13-qp18.mp4</BaseURL><BaseURL phase=“14” label=“batman phase 14 qp18”>batman-phase-14-qp18.mp4</BaseURL>   </Representation>  ... </Representation>  </AdaptationSet> </Period> </MPD>

FIG. 20 is a flowchart illustrative of additional blocks, steps and/oracts with respect to an example tile selection and bandwidth annealingprocess according to an embodiment of the present invention. In onearrangement, a knapsack combinatorial optimization may be used for tileselection and annealing based on the inputs comprising gaze vectors,bandwidth allocation/limitation, stream weights, etc., as pointed outpreviously. At block 2002, process 2000 executing at a server or nodeassociated with video optimization commences with or responsive toreceiving a request for a 360° immersive video session. At block 2004,process 2000 proceeds to retrieve or otherwise obtain tiled streammanifest definitions so as to be able to determine all aspects of thevideo characteristics based on deep-level inspection and processing inorder to extract the needed tiles, which may be effectuated by way ofparsing the steam manifests (block 2006). A grid layout is determinedfor each stream, e.g., columns and rows per frame (block 2008). In anexample variation, process 2000 may register with a network managementand orchestration node to receive notification messages relative toallocated/determined bandwidth for the requested session (block 2010).If a bandwidth allocation is received (block 2012), a furtherdetermination may be made whether gaze vector information is received(block 2014). Thereafter, tile weights are determined based on the gazevector information (block 2016). Tile selection may be performed as aknapsack annealing process responsive to available bandwidth allocationnotification (block 2018). At block 2020, selected tiles are provided toa tile stitching process (executing at the server or at the clientdevice).

FIGS. 21A and 21B are flowcharts illustrative of additional blocks,steps and/or acts with respect to further aspects of a tile selectionand bandwidth annealing process according to an example embodiment ofthe present invention. In particular, process 2100A shown in FIG. 21Aexemplifies a relatively simpler knapsack annealing process, which maybe computationally more expensive that can result in about approximately1 second for tile splicing. At block 2102, the tiles are initialized toa lowest quality. An adequacy metric may be determined as a ratiobetween a stream variant weight and a tile weight, which may be providedwith respect to all <tile,GOP>-tuples or combinations (block 2104). Adetermination is made with respect to upgrading the <tile, GOP>-tuplehaving the least adequacy (i.e., most inadequacy), as set forth at block2108. A determination is made whether a transmit buffer model isviolated or satisfied (block 2110). If the buffer model is not satisfied(i.e., violated), that tile/GOP combination may be disqualified forupgrades and the process flow returns to considering the next tile/GOPcombination for upgrading, as set forth at block 2112. If the buffermodel is not violated, the tile/GOP combination is upgraded in quality(block 2114). The foregoing process may be iteratively performed untilthere are no non-disqualified tile/GOP combinations at less than maximumquality (block 2116). If none, process 2100A is completed by sendingselected tiles to a tile mux and stream generation process, as set forthat block 2118.

Turning to FIG. 21B, a performance-optimized tile selection andannealing process 2100B is shown, which in some implementations mayresult in faster tile section, resulting in overall tile splicing timesaround 10 milliseconds or so. Broadly, a penalty factor may be imposedwith respect to I-tile upgrades (which are costlier than P-tile upgradesas I-tiles pack more data) and a “naïve” upgrade sequence may precedeinitially where tile upgrades are not checked against the transmitbuffer model regardless of whether the upgrades comply with an adequacymetric. Further, as tiles in the ROI/viewport get upgraded first and therest of the tiles of a frame are upgraded/updated subsequently, anexample embodiment may factor in a penalty based on where the tileposition is. For example, if the tile position is close to the gazevector, the penalty associated with that position may be lower. Further,penalty may also be related to the tile position as a balance betweenthe quality/type of the tile to be upgraded vs. where it is in theframe. The effects of a penalty factor or combination may beincorporated in the annealing process by suitably modulating theadequacy metric used in the naïve upgrade sequence in an exampleembodiment.

Similar to the embodiment of FIG. 21A, the tiles of all video encodingsare initialized to a lowest quality (block 2132). An adequacy metric maybe determined as a ratio between a stream variant weight and a tileweight, multiplied by a penalty factor, which may be provided withrespect to all <tile,GOP>-tuples or combinations (block 2136). At block2134, a heap structure (e.g., as a large pool of memory) may beconfigured for containing adequacy values for all <tile,GOP>-tuples. Atblock 2138, a least adequate tile is pulled from the heap and recordedon a naïve upgrade sequence or process. If the tile quality can beupgraded more (block 2140), it is performed and an adequacy metric forthe upgraded tile is determined (block 2142). The foregoing process maybe executed in an iterative loop until the heap is empty and all thetiles that can be upgraded have been upgraded (block 2144). A binarysearch sequence may be effectuated to on the naïve sequence to find alast valid state that obeys a given transmit buffer model (block 2146),which may be used as a starting tile state (block 2148). A new upgradeheap may be configured for containing the tile/GOP states (block 2150).A least adequate tile/GOP combination is pulled from the heap (block2152) and validated against the transmit buffer model (block 2154). Ifthe pulled tile/GOP cannot satisfy the buffer model, it is disqualifiedfrom future upgrades (block 2158). Otherwise, a determination is made ifit can be upgraded more (block 2156). If so, an adequacy value for theupgraded tile/GOP combination that satisfies the transmit buffer modelis determined (block 2160). The foregoing operations are performediteratively until the new upgrade heap is empty, as set forth at block2162. If so, process 2100B is completed by sending selected tiles to atile mux and stream generation process, as set forth at block 2164.

Example annealing processes set forth herein advantageously facilitategradual refreshing of frames when a viewport or bandwidth is changed,thereby allowing for the ability to minimize latency in increasingquality based on a user's field of vision and at the same time notoverload the bandwidth. Typically, when attempting to perform qualitychanges on all tiles at the same time, several issues may be encountereddue to the result of changing P-tiles for I-tiles at the same time,which are expensive in terms of encoded bitrate. On the other hand,performing this substitution with a minimal client buffer can cause toomuch delay in delivering the I-slices/frames.

In an example embodiment that employs gradual refreshing, the videostreams do not have I-frames (except for the initial I-frame or anyother special frames like Instant Decode Refresh or IDR frames).Instead, a video stream has I-blocks or I-tiles that may be distributedthroughout a time sequence so that any particular spot on the screengets an I-block at regular intervals, e.g., by way of phase-encodedstreams as described in detail in the earlier sections of the presentpatent application. Thus, in such a scenario, there is no frame whereall the pixels are refreshed by I-blocks. By performing gradual refreshannealing, example embodiments of the present invention can beadvantageously configured to level out frame sizes (i.e., in terms ofthe amount of coded image data) and reduce the bandwidth consequences ofinjecting an I-frame to upgrade the quality of tiles that enter the FoVor viewport. Whereas a PE scheme may allow selective early refreshes ofa tile in a time/frame sequence, it may impose certain bandwidth cost(e.g., due to having multiple I-tiles in a frame, which can cause anincrease in the required bandwidth for that time interval correspondingto the transport of that video frame). However, an example embodimentinvolving PE can be configured such that the advantage of having asteadier level of bytes/frame overweighs such costs.

Over time in a frame sequence, a PE-based embodiment may allowmanipulation of the phases of the various tiles around until the I-tilesare roughly evenly distributed in time again. Such a capability can beconfigured to be user- and/or content-dependent with respect to whenthis redistribution occurs as it requires the user to keep their fieldof view steady long enough for it to occur. In order to choose tiles tofill the bandwidth, an example embodiment may involve modeling the bytesizes of frames stretching 3 GOPs into the future (this choice isarbitrary) and performing hypothetical early refreshes (HER) based onthe buffer model (e.g., with 3 GOPs in a look-ahead scenario). Based onthe embodiments set forth in FIGS. 21A and 21B, it can be seen that sucha process starts by picking the minimum-quality stream for all the tilesand then considers each GOP of tiles, both for the current frame andfuture frames, and evaluates whether upgrading that GOP will violate anybandwidth constraints (which are a combination of individual frame sizesand buffer considerations). If considering upgrading a current (asopposed to future) tile-GOP combination above the quality of analready-delivered I-frame, an embodiment of the present invention maytemporally realign this tile to start with an !-frame (which may affectthe rest of the frames in a splicing window). Once the list of possibleupgrades is obtained, they may be weighted according to the quality andthe tile's position in the FoV (so tiles near the center of vision willbe favored for upgrades). In one implementation, the foregoing upgradestep may be repeated until buffer constraints make any more upgradesimpossible.

It should be appreciated that an example upgrade process may move aroundin time and in space depending on the look-ahead GOP modeling. In onearrangement, each tile may have a 3-4 GOP horizon, which can each beupgraded as the process is iterated, where future GOP upgrades are forpotential future enhancements for early refreshes covering 3-4 GOPs into the future.

In considering a HER-based implementation, a few potential metrics maybe identified and/or employed to obtain a suitable trade-off: (i) deadair, (ii) maximum buffer level, and (iii) end buffer level, amongothers. In one example implementation, the maximum buffer level may beweighted as a leading criterion for HER upgrades where adequatebandwidth may be freed up to allow tile-GOP quality upgrades.

As set forth in the embodiment of FIG. 21B, once the end is reached inthe upgrading iterations, a slice/frame can be muxed using a set oftiles, whereby the byte size of the muxed slice/slice may be calculatedand its effect on the transmit buffer may be recorded so that the nextslice/frame is accurately constrained in accordance with the giventransmit buffer model. When the next time a frame is spliced (e.g., theuser gaze has changed, thereby causing adjustments to be made), theknapsack annealing process may be repeated wherein one extra frame ismodeled relative to the previous operation, which can validate and/orfine-tune the knapsack/annealing process.

Skilled artisans will recognize that a heap memory structure employed inthe embodiment of FIG. 21B is particularly advantageous for keepingtrack of upgradable tiles because recalculating the score of thetile-GOP upgrades on every iteration may be avoided. As notedpreviously, an adequacy metric is defined for scoring tiles, which isused in choosing which tile to upgrade, wherein parameters such asvariant_weight, tile_weight and penalty are provided in a suitablemathematical relationship to capture a desirable upgrade scenario. Assuch, the variant_weight parameter may be defined as a property of anencoded stream and higher quality stream variants (having lower QPs)have a higher variant_weight. Some example variant weights are {1/QP},{100-QP}, or a value defined in the manifest examples set forth above,or it could be the bitrate of the entire stream. The tile_weight mayalso be provided as a function of the tile's position relative to thegaze as set forth above. In general, tiles in the user's direct FoV orROI/viewport may be accorded higher tile_weights. The example adequacymetric formulation set forth in the embodiments of FIGS. 21A/B isconfigured such that as the stream quality increases, the adequacy valuealso increases, and the tiles closer to the gaze vector have loweradequacy than tiles of the same quality farther from the gaze vector(which configures the annealing process to upgrade tiles closer to thegaze vector before upgrading tiles away from the gaze vector).

Further, example embodiments also include a penalty factor in scoringthe tiles for an upgrade process as noted above. In one arrangement, apenalty may be imposed when an early refresh with an I-tile is requiredwherein a tile in the current GOP is to be upgraded beyond the qualityit had in the previous slice/frame. Such a penalty has the effect ofincreasing that tile's adequacy which delays the upgrade relative toother tiles in the heap. This allows tile upgrades when the gaze haschanged enough but defers early refreshes in marginal cases.

It will be apparent to one skilled in the art thatadditional/alternative formulations may also be used for scoring tileupgrades in some variations within the scope of the present invention.

FIG. 22 is illustrative of a transmit buffer model process for use in atile selection and bandwidth annealing arrangement according to anexample embodiment of the present invention. In general, a transmitbuffer model may be configured to be consistent with a frame ratedepending on the implementation (e.g., 30 fps, 60 fps, etc.), wherein atemporal variation of how data is added into and transmitted out of abuffer may be parameterized in order to determine whether and when theremight be an overflow (i.e., a violation). In the example transmit buffermodel 2200, b₀ is starting buffer level, b_(i) is the size of bufferbefore adding an access unit or NAL unit, n_(i) is the size of theaccess/NAL unit, and a_(i) is the size of buffer after adding anaccess/NAL unit, where a_(i)=b_(i)+n_(i), for i≥1. Assuming a transmitrate of r, and Δt=1/frame rate, the following relationship obtains:b _(i+1)=Max{0,a _(i) −r(t _(i+1) −t _(i))}

A buffer_size parameter may be defined as follows:buffer_size=r(latency_frames)Δt

According to the foregoing model, if Max(ad >buffer_size, it may beindicated as a buffer overflow condition. Thus, as different n_(i) arebeing added pursuant to a tile upgrade process, the buffer end pointlevel can be checked against a calculated buffer size in order to insurethat no buffer violations are engendered in the upgrade process.

Turning to FIG. 23, depicted therein is an arrangement 2300 where aclient UE device may be configured to perform certain aspects of 360°immersive video optimization for purposes of an embodiment of thepresent patent disclosure. User 2310 having a suitable 360° displaydevice is operative with a connected UE device 2302 that includes avideo optimization client module 2306 and a connected player 2308disposed to generate suitable playback signals to the display device. Inone embodiment, player 2308 may comprise an HEVC or AV1 playerconfigured with appropriate video decoder 2314, display renderer 2316,audio decoder 2318, and sound renderer 2320. Similar to an exampleembodiment set forth hereinabove, a gaze tracking module 2312 may beprovided with the connected UE device 2302, which may be configured toconsume 360° immersive video content delivered over the Internet 2304 inan ABR streaming environment.

Client optimization module 2306 preferably includes a 360° immersivevideo interface module 2321 comprising a manifest parser 2328, a videotile and audio stream downloader 2330, a bandwidth estimation module2326 and a tile selection module 2324, which may be configured tooperate in a manner similar to the embodiments set forth hereinabovewith suitable device-centric modifications, mutatis mutandis. An HEVCtile/audio request 2344 may be generated to a network location, e.g., acontent provider network or a cloud-based storage, via the Internet2304, based on a manifest 2340 with respect to a particular content.Requested video tiles and audio data may be received via path 2342. Gazevector information provided to the immersive video interface module 2321from the gaze tracking module 2312 (e.g., via path 2322) may be utilizedalong with bandwidth estimation in selecting tiles per frame, which maybe provided via a video signal path 2331 to a dynamically allocatedvideo buffer 2332. Likewise, corresponding audio segments may beprovided to an audio buffer 2336 via an audio signal path 2338. Tiles ofdifferent qualities may be provided to a tile combiner 2334, whichgenerates a muxed encoded video stream 2346 to the player's videodecoder 2314. Encoded audio stream 2348 may be generated from the audiobuffer 2336 to the audio decoder 2318. Decoded audio and video dataprovided to the respective renderers 2320, 2316 of the player 2308 arerendered appropriately for display/presentation in an immersiveenvironment effectuated by the user's display device, essentiallysimilar to the example embodiments set forth previously.

FIG. 24 depicts a block diagram of a computer-implemented apparatus thatmay be (re)configured and/or (re)arranged as a platform, node or elementto effectuate one or more aspects of 360° immersive video processing,preparation and tile selection optimization according to an embodimentof the present invention. Depending on implementation and/or networkarchitecture, apparatus 2400 may be configured or otherwise integratedin different arrangements suitable for operation at one or morehierarchical levels of an example environment (e.g., as shown in FIGS. 1and 2). One or more processors 2402 may be provided as part of asuitable computer architecture for providing overcall control of theapparatus 2400, wherein processor(s) 2402 may be configured to executevarious program instructions stored in appropriate memory modules orblocks, e.g., persistent memory 2408, including additional modules orblocks specific to media preparation, preprocessing, BIE/PE-based tileencoding including adaptive bitrate encoding/transcoding, optimized tileselection and bandwidth annealing, tiled media packaging, tilestitching, etc. as described in detail hereinabove. For example, suchmodules may include tile-based PE/BIE encoder 2404, ABRencoder/transcoder 2406, GV processing and tile weight processing module2413, tile selection and annealing module 2416, packager and manifestgenerator 2410, projection mapper 2418, and the like. Also, a packagedmedia database 2419 may be provided in an example embodiment dependingon the implementation of apparatus 2400. Accordingly, various networkinterfaces, e.g., I/F 2414-1 to 2414-L, operative for effectuatingcommunications with network infrastructure elements including video backoffice elements, DRM entities, origin servers, client controller nodes,source media nodes, management nodes, and cache databases as well asinterfaces 2412-1 to 2412-K for effectuating communications sessionswith one or more downstream nodes, e.g., including delivery servers,DSLAM/CMTS elements, RAN infrastructure elements, premises gatewaynodes, etc., may be provided as part of the apparatus 2400 depending onthe network hierarchical level and/or integration.

FIG. 25 depicts a block diagram of an example client UE device orsubscriber station 2500 configured for performing various client-sideprocesses according to one or more embodiments of the present patentdisclosure. Client device 2500 is generally representative of variousviewing devices illustrated in one or more Figures described above, andmay include appropriate hardware/software components and subsystemsconfigured for performing any of the device-side processes (eitherindividually or in any combination thereof) with respect to mediarequest generation, gaze vector generation, tile selection and bandwidthestimation, among others, depending on implementation. One or moremicrocontrollers/processors 2502 are provided for the overall control ofthe client device 2500 and for the execution of various stored programinstructions embodied in one or more persistent memory modules that maybe part of a memory subsystem 2511 of the device 2500. For example, 360°immersive video client applications 2513A including VR applications maybe operative with a bandwidth estimator 2513B and associated tileselector 2513C, that may be provided as part of the memory subsystem2511. A manifest parser 2517 may be provided to facilitate thegeneration of media requests to appropriate locations.Controller/processor complex referred to by reference numeral 2502 mayalso be representative of other specialty processing modules such asgraphic processors, video processors, digital signal processors (DSPs),and the like, operating in association with suitable video and audiointerfaces (not specifically shown). Appropriate network interfaces suchas network I/F modules 2504 and 2506 involving or operating with tuners,demodulators, descramblers, MPEG/H.264/H.265/AV1 decoders/demuxes may beincluded for processing and interfacing with IPTV and other contentsignals received via a DSL/CMTS network 2598 or a satellite network2596. Where an STB is configured as an example client device orapplication, suitable demodulators may also be included. One or moremedia players 2514 may be provided for operating in conjunction with theother subsystems of the client device 2500, e.g., user interface 2520,which may be further configured with additional subsystems forfacilitating user control over media playback, including channel changerequests and any trick mode operations. For example, client/user controlfunctions may include pausing, resuming, fast forwarding, rewinding,seeking, bookmarking, etc. with respect to a particular 360-degreeimmersive video asset that is being played. Example media players may beconfigured to operate with one or more A/V coder/decoder (codec)functionalities based on known or hereto unknown standards orspecifications.

Other I/O or interfaces such as an immersive display interface 2515,touch screen or keypad interface 2520, USB/HDMI ports 2518, Ethernet I/F2508, and short-range and wide area wireless connectivity interfaces2512 may also be provided depending on device configuration. Variousmotion detection and gaze tracking sensors 2516 may also be included,some of which may comprise gyroscopes, accelerometers, position sensors,etc. A hard disk drive (HDD) or local DVR system 2510 may be included inan example implementation for local storage of various program assets. Asuitable power supply block 2522 may include AC/DC power conversion toprovide power for the device 2500. It should be appreciated that theactual power architecture for the device 2500 may vary by the hardwareplatform used, e.g., depending upon the core SoC (System-on-Chip),memory, analog front-end, analog signal chain components and interfacesused in the specific platform, and the like.

In further aspects of the present invention, embodiments are set forthbelow relating to inserting various types of secondary content, e.g.,third-party sponsored content and advertisement content including stillimages, video clips, graphic text images, etc., collectively referred toas advertisement content or “ad content” for short, into a 360-degreeimmersive video playback environment in a symbiotic and seamless manner.In particular, embodiments are disclosed where one or more of thefollowing technical problems are advantageously overcome. For example,in current video streaming technologies involving secondary content, adinsertion generally degrades the immersive experience of the originalvideo, especially if the secondary content being inserted is not a360-degree video. Even if the ad content were a 360-degree video, theuser would typically be watching the video using an HMD unit and wouldbe compelled to watch the ad content up close, potentially losing allthe impression of being immersed in another world, i.e., the virtual 3Ddisplay experience, that the original video might have built up so far.Further, ad insertion typically takes place at the bottom of the videoframe, which may cover up or block regions of interest in the originalvideo (even if the overlaid ad content were somewhat transparent), andthus also destroy the 360-degree immersive feel of the video asset beingplayed.

Broadly, embodiments herein may be advantageously configured to leveragean exemplary tile-based encoding scheme set forth in detail hereinabovewherein a video frame to be assembled from a plurality of tiles may bemanipulated or otherwise analyzed prior to tile muxing/stitching foridentifying some of the tiles that may be replaced by secondary or adcontent that is also encoded/transcoded into tiles. In one embodiment,the determination as to which video tiles to use for ad contentreplacement may be based on a fixed selection made by the contentcreator or editor beforehand. In another embodiment, video tileselection for ad replacement may be performed dynamically based on thegaze vector information that is reported back by the client device asthe 360-degree immersive video is being played out. In a furtherembodiment, a combination of both schemes may be implemented forselecting a portion of the video tiles of a frame for replacement by adcontent tiles. Additional details regarding the foregoing embodimentsare set forth below.

As noted previously in reference to tile-based encoding of source video,a 360° video frame may be partitioned into a rectangular array or gridof blocks or tiles that can be independently encoded/decoded and evenallow for random access to specific regions. By way of reference, avideo frame comprising a 16-by-8 array of 128 tiles was shown in FIG. 4Cwith respect to a 4K video asset frame 400C, wherein the tiles may ormay not be spaced evenly as previously noted. Further, in an embodimentof the present disclosure, tiles may be selected from either BIE-basedstreams or PE-based bitstreams, as described in detail hereinabove withrespect to a number of Drawing Figures, e.g., FIGS. 5-12. In oneimplementation, each ad content tile may be first coded as an I-tile tobe included in a BIE frame (i.e., X frame having a P-slice header andcomprising blocks of intra-coded data (e.g., I-tiles or I-blocks), or inthe first I-frame of a GOP. Subsequently, the advertisement for which anI-tile has already been included in the previous frame may be sent as aP-tile in the BIE-based P-slices. As noted above, this encodingtechnique enables mid-GOP changes in frames, even those includingadvertisement content tiles. Accordingly, various types of secondarycontent tiles may be added, removed or updated mid-GOP in a videosequence. Skilled artisans will recognize upon reference hereto thatthis capability provides very high fidelity to an ad content policy thatmay be configured based on content provider policies and/or networkoperator policies. An implementation of ad insertion according to anembodiment may be configured such that individual ad delivery can besatisfied within a tight timing tolerance or requirement, e.g., thestart and end times of an ad be met within a range of 1-second in anillustrative scenario. For instance, if the ad content policy requiresthat a tile-based ad start at 2 minutes and 3 seconds (00:2.00:03) afterthe start of the video and end at 2 minutes 4 seconds (00:2.00:04), anembodiment of the present invention can adhere to this ad timing window,within a few milliseconds on either end (i.e., a tiny fraction ofvariance at the start time and/or the stop time).

To illustrate the inventive concepts relating to ad insertion accordingto the teachings of the present disclosure, reference is now taken toFIGS. 28A-28C that depict example display scenarios with respect toinserting advertisement content in a 360° immersive video environment.In particular, FIG. 28A shows an example unwrapped frame 2800A from a360° immersive video asset, which illustrates a rectangular array ofvideo tiles that are individually numbered, e.g., 128 tiles, orotherwise uniquely identified. Imagine that an object, e.g., airplane2803, in the video flies from left to right and is currently in thecenter and forms the object of interest. A region 2802A surrounding theobject 2803 may comprise any shape (e.g., a circular region, anelliptical region, a square region, etc.) that may be indicative of theuser's direct FoV or viewport depending on the display unit. By way ofillustration, tiles that are within the region 2802A or at least on theperiphery thereof, e.g., Tiles 7, 8, 9, 10, 22, 23, etc., therefore forma region of interest for purposes of analyzing and/or determining whichtiles therein may be available or replaceable for inserting secondarycontent tiles according to an example embodiment. Video tiles outside ofthe region will be wrapped around the user's FoV (or form a display areathat needs to be panned before becoming visible to the user).Accordingly, some of the video tiles of the frame may be beyond theuser's peripheral vision, and some may even comprise the area directlybehind the user's gaze when he is looking in the direction of the objectof interest, e.g., plane 2903. In the example video frame 2800A, theregion of interest or the part where the most interesting thing ishappening is therefore near the immediate vicinity or around the plane.On the other hand, tiles near the bottom periphery of the FoV such asTiles 87, 88, 89, 90, 104, 105 can serve as locations for one or moreads that are directly visible to the user (since they fall within theFoV or on its periphery). Furthermore, the remaining video tiles outsideof the FoV may also serve as locations for ads that will be visible ifthe user looks around during the scene. In one embodiment, tiles orother regions of video frames that contain little or low action ormotion, e.g., static areas, may be analyzed and/or determined so as toearmark certain tile locations as being suitable for replacement bysecondary/ad content.

FIG. 28B depicts a video frame 2800B that is the same frame 2800Adescribed above but serves to demonstrate an example of tilelocation-based ad insertion therein where one or more tiles are replacedby ad content tiles. In one embodiment, an ad content object, which maycomprise a still image, a logo or slogan, or part of a secondary videoclip, may form a single tile. In another embodiment, ad content objectsmay take up a number of contiguous tiles. Depending on how much “realestate” is available in the region comprising FoV 2802B, eithersingle-tile ads (e.g., smaller ads) or multi-tile ads (e.g., larger ads)may be placed within the user's line of sight. Likewise, regions outsideFoV 2802B may also include tile locations that may be replaced by adcontent tiles. By way of illustration, contiguous Tiles 98, 99 and 100are replaced by a multi-tile ad object designated AD-1A. Likewise, asecond set of contiguous Tiles 109, 110 and 111 are replaced by anothermulti-tile ad object designated AD-1B. As a further illustration, singletile ad objects AD-2A, AD-2B and AD-2C are placed at locationscorresponding to Tiles 54, 59 and 88, with Tiles 54 and 59 falling onthe border of FoV 2802B whereas Tile 88 falling completely inside FoV2802B but away from the object of interest, e.g., plane 2803.

FIG. 28C depicts an example video frame 2800C that comes later in avideo sequence as the playout progresses in time, which demonstrates thedynamic nature of ad insertion in accordance with the teachings of thepresent disclosure. As the object of interest 2803 moved toward right,corresponding FoV 2802C has also moved, thereby resulting in a differentset of tile locations within FoV 2802C that are suitable for adreplacement. By way of illustration, Tile 94 falling entirely in FoV2802C is replaced by an ad object AD-3A and Tile 96 falling on theborder of FoV 2802C is replaced by an ad object AD-3B. Some of the tilesthat were unavailable for ad insertion in the previous FoV 2802B are nowavailable for ad insertion, e.g., Tiles 40, 41, 56 and 57. Tile 54 thatfell on the border of the previous FoV 2802B continues to be availablefor ad insertion, now showing an ad object designated as AD-4A.

One skilled in the art will recognize that it is not necessary to havedifferent ad objects being placed in the video frames as the playoutprogresses in time. In some embodiments, whereas some ad objects maypersistent over a portion of the runtime of a video asset, other adobjects may be configured to be more ephemeral, e.g., depending on thevideo/ad content provider policies, network operator policies,subscriber profiles, and the like. Further, some ad objects may becontextualized with respect to the contents of the video being playedout as well as personalized and/or targeted to the users based onpreferences, demographics, etc.

It will be apparent that choosing the right video tiles for replacementis critical to maintaining a good quality of experience when aparticular 360° immersive video asset is being watched. As notedpreviously, in a typical 360° immersive video playback environment,there is generally a small number of areas of a frame where most of theaction is taking place, e.g., regions of interest, which may varydepending where the viewer is looking. Although a viewer can look aroundthe 360° immersive video display space, at any given time there areareas that the viewer would be focusing on the most. Accordingly, whileit is imperative not to replace tiles which are in the center of aregion of interest in a scene with ads, which may vary depending on thegaze vector information, a lot of other regions in the 360° scene canserve as good locations for ad insertion (i.e., eligible tilelocations).

In accordance with the teachings of the present disclosure, a number oftile eligibility schemes may be provided for identifying which of thevideo tiles of a 360° frame can be replaced by secondary/ad content. Byway of illustration, following embodiments exemplify three schemes,without limitation, for purposes of the present patent application. Inone embodiment, a content provider may provide a tile metadataspecification that specifies for each tile an array of start and endtimes relative to a known timing reference, e.g., the runtime of a videoasset, as to when the tile can be replaced by an ad content tile.Referring now to FIG. 27, shown therein is an example tile metadataspecification 2700, which in one embodiment may be generated as part ofmedia preparation and packaging processes set forth hereinabove inreference to FIGS. 1 and 2 above, that illustrates tile-specific adinsertion eligibility timing windows for each of a plurality of tiles ofa video frame (e.g., on a tile-by-tile basis). As illustrated, 128 tiles2702-1 to 2702-128 having respective Tile ID information 2704 are shown,each having a corresponding row of eligibility timing window 2705-1 to2705-128, collectively designated as ad availability timing information2706. In an example scenario of a video asset having a 5-minute runtime,each eligibility timing window array or row 2705-1 to 2705-128identifies a plurality of timing windows for a particular tile ID valueas a set of tuples of start and end times within the 5-minute periodwhen the tile location can be used for ad insertion. In one example, thetiles of a frame may be assigned unique IDs sequentially from left toright and top to bottom of the tile grid forming the frame. By way ofillustration, Tile 1 is provided with an eligibility timing window array2705-1 that comprises three timing windows 2708-1, 2708-2 and 2708-3,each having a respective start and end time. Timing window 2708-1specifies that Tile 1 may be used for replacement from 1.0 second intothe video till time=3.0 seconds. Likewise, timing window 2708-2specifies that Tile 1 may be used again at 3 minutes into the video for5 more seconds and timing window 2708-3 specifies that Tile 1 may beused yet again at 4 minutes into the video for 6 more seconds forreplacement. On the other hand, Tile 128 may be used throughout the5-minute video for ad insertion, as indicated by the single entryeligibility/availability timing window array 2705-128.

Skilled artisans will recognize upon reference hereto that although theforegoing tile metadata specification 2700 illustrates ad availabilitytiming data based on video runtime information, additional/alternativeembodiments may be based on other types of timing data such as, e.g.,presentation timestamp (PTS) information, decoding timestamp (DTS)information, program clock reference (PCR) information, system clockreference (SCR) information, a wall clock reference information, and/ora Global Positioning System (GPS) timing reference information, etc.

In another embodiment, rather than using a fixed metadata specification,eligibility selection may be dynamically determined based the gazevector information reported by the client device, which has beendescribed in detail hereinabove in reference to a number of DrawingFigures, e.g., FIGS. 15A-B to FIGS. 16A-16C. As set forth previously,3-dimensional gaze vector information (normalized or non-normalized) maybe used to determine or otherwise define a FoV and accordingly identifywhich tiles fall completely within the FoV. A subset of the tilesfalling within the FoV and determined not to contain one or more objectsof interest inside the FoV may be selected for replacement bysecondary/ad content. Skilled artisans will recognize that the advantagein selecting tiles based on gaze vector information is that unlike thefixed metadata specification technique it doesn't require a priori fixedtiming windows on a tile-by-tile basis and hence can be used for liveevents. As the user looks around, the ads may be reorganized but maybriefly appear in the center of the FoV if there are sudden changes inthe gaze. On the other hand, an embodiment based on fixed metadataspecification, which is more suitable for 360° immersive VOD/MOD contentwith respect to facilitating ad insertion during runtime, may beconfigured to avoid such a situation by precisely defining applicabletiming windows.

Another embodiment of the present invention may comprise a combinationof both fixed metadata specification and gaze vector information. In anexample implementation, the video tiles may be initially selected basedon the gaze vector information but then filtered according to the tilemetadata specification so as to not inadvertently replace tiles in aregion of interest. Yet another embodiment may involve further pixeldata analysis on a tile-by-tile basis, either separately or incombination with any of the foregoing schemes, to further refine tileeligibility for ad replacement.

FIGS. 26A-26C depict flowcharts illustrative of various blocks, stepsand/or acts relative to inserting advertisement content in a 360°immersive video asset during playout that may combined according to oneor more embodiments of the present invention consistent with at least aportion of the foregoing teachings. Process 2600A of FIG. 26A commenceswith receiving a request from a client device for playing a particularimmersive video asset, as set forth in block 2602. As previously noted,each video frame of the video asset may comprise an array of tilesprojected on a 3-dimensional (3D) display environment viewed by a useroperating the client device. At block 2604, a plurality of video tilesof the particular immersive video asset are selected to be assembled asa video frame for delivery to the client device. As previously describedin detail, the plurality of video tiles of the particular immersivevideo asset may be selected from one or more tile-encoded bitraterepresentations of the particular video asset, based on either PE-basedor BIE-based encoding, wherein each bitrate representation has aseparate video quality that is controlled by a quantization parameter(QP) value used for each bitrate representation. At block 2606, aportion of the video tiles are identified that can be replaced with acorresponding set of advertisement content tiles, which may begenerated, encoded and/or transcoded from appropriate source files ofstill images, video clips, etc. At block 2608, the portion of the videotiles identified as being eligible for replacement may be replaced withthe corresponding set of advertisement content tiles. At block 2610, thecomplete video frame is muxed and assembled that includes theadvertisement content tiles at select locations, which is thentransmitted to the client device.

Process 2600B of FIG. 26B sets forth additional blocks, steps and/oracts that may be combined within process 2600A described above. At block2622, a tile metadata specification may be obtained, accessed orotherwise analyzed that identifies advertisement insertion availabilitytiming information with respect to each of the plurality of video tilesof the video frame. Responsive to the advertisement insertionavailability timing information, the portion of the video tiles eligiblefor replacing with the advertisement content tiles are then selected orotherwise identified (block 2624). At block 2626, suitable ad contentfiles are obtained for replacing and multiplexing with the remainder ofthe video tiles, which are provided to a tile stitching and streamgeneration process (block 2628). At block 2630, the process flow maycontinue depending on whether additional video frames need to beprocessed during the runtime of the video asset.

Process 2600C of FIG. 26C sets forth additional blocks, steps and/oracts that may be combined within process 2600A described above. At block2642, a gaze vector from the client device is obtained relative to theparticular immersive video asset, the gaze vector defining a field ofview (FoV) in the 3D display environment with respect to where the useris viewing in reference to a projected video frame. Responsive to thegaze vector, the portion of the video tiles eligible for replacing withthe advertisement content tiles may be selected or otherwise identified(block 2644). Similar to process 2600B, suitable ad content files areobtained for replacing and multiplexing with the remainder of the videotiles, which are provided to a tile stitching and stream generationprocess (blocks 2646 and 2648). At block 2650, the process flow maycontinue depending on whether additional video frames need to beprocessed during the runtime of the video asset.

FIG. 30 is a flowchart of various blocks, steps and/or acts relative torelative to inserting advertisement content in a 360° immersive videoasset during playout according to a combination process 3000 of thepresent invention in one example embodiment. Similar to block 2602 inprocess 2600A above, process 3000 commences with receiving a requestfrom the client device with respect to a particular 360-degree immersivevideo asset (block 3002). At block 3004, a gaze vector is received fromthe client device. At block 3006, a plurality of video tiles (e.g., 128tiles in a 4K video frame) of the requested video asset are selected tobe assembled into a video frame for delivery to the client device. Atblock 3008, various sets or groups of tiles relative to the FoV based onthe gaze vector are identified or otherwise determined. For example, afirst set (Set A) of tiles may comprise tiles that fall entirely in theFoV, a second set (Set B) of tiles may comprise tiles that are partiallyin the FoV (i.e., tiles that fall on the FoV's border), and a third set(Set C) of tiles that fall outside of the FoV. At block 3010, a decisionor determination is made as to whether a tile metadata specification isavailable for the requested video asset. If so, tiles identified asbeing unavailable for ad insertion per current video runtime are removedfrom further eligibility analysis (block 3012). Otherwise, all the tilegroups identified in block 3008 may be considered for ad insertioneligibility. Accordingly, either a filtered selection of the tiles fromSets A through C or complete selection of tiles from Sets A through Cmay be considered for replacement eligibility based on ad content policyconfiguration, tile image activity, content provider policyconfiguration, etc. Responsive to the eligibility analysis, a certainnumber of tiles from each set may be identified and/or obtained forreplacement and may be replaced as set forth at block 3014. Forinstance, “x” number of tiles in Set A, “y” number of tiles in Set B and“z” number of tiles in Set C may be replaced by corresponding ad contenttiles as previously described. Thereafter, at block 3016, selected adcontent tiles and the remaining video tiles may be provided to a streamgenerator for assembling into a frame using any of the tile stitchingand stream generation schemes set forth earlier in the present patentdisclosure. Subsequently, the assembled frame is delivered to the clientdevice (block 3018). A determination may be made whether there are moreframes in the video sequence of the requested video asset (block 3020).If so, process flow returns to block 3004 to continue receivingsubsequent gaze vector information. Otherwise, process 3000 isterminated (block 3022).

FIG. 29 depicts a system or apparatus that may be implemented in a 360°immersive video network portion 2900 for facilitating advertisementinsertion in accordance with an embodiment of the present invention.Skilled artisans will recognize that network portion 2900 is roughlysimilar to portions of the network architectures shown in FIGS. 1 and 2.A network node or element 2902 may be configured as a video serveroperative in conjunction with a back office functionality and/or 360°video optimization functionality as set forth in the network portion ofFIG. 2. Video server 2902 is further operative to interface withappropriate 360° video asset repositories 2922 (which may includedifferent bitrate representations of tile-encoded media having varyingqualities, and tile metadata specifications where provided) as well assuitable delivery server infrastructure (not specifically shown in thisFIG.) to facilitate video session setup control, bearer delivery, gazevector processing, etc. in a computer-implemented platform similar tothe apparatus 2400 shown in FIG. 24. Accordingly, suitable modules suchas asset manager including video tile selector 2904, ad content tileselector 2906, tile mux/stream generator 2907, session manager 2908 andgaze processor 2910 may be configured to operate under processor controlto facilitate video tile replacement eligibility logic, ad contentinsertion logic, ad content retrieval, etc. according to the embodimentsset forth herein, wherein one or more client devices 2812A, 2812B areoperative with respect to requesting respective 360-degree video assetsto be displayed in conjunction with suitable display units associatedtherewith.

As noted previously, secondary/ad content may comprise various types ofdigital assets including but not limited to still images, graphic textboxes, short video clips, etc., which may or may not be tile-encoded. Anad server 2918 may be provided with suitable encoding/transcodingfunctionality to generate ad content tiles in a suitable formatcompatible with the tile encoding scheme used for generating 360° videoassets. Accordingly, similar to the coding schemes set forth hereinabovewith respect to source media preparation, ad content tiles may begenerated using at least one of HEVC H.265 compression, AV1 compression,H.266 Versatile Video Coding (WC) compression and/or Future Video Codec(FVC) compression. Ad tile selection module 2906 is operative toretrieve or obtain suitable ad content tiles via interface 2920 from thead server 2918 at appropriate runtimes with respect to one or moreon-going 360-degree video sessions. Tile mux/stream generator 2907 isconfigured to assemble the requested video asset tiles and selected adcontent tiles into muxed frames that may be delivered to respectiveviewers under appropriate session manager control. Accordingly, by wayof illustration, each client device 2912A/2912B is operative to initiatea video session and receive corresponding 360° video stream inrespective sessions 2914A/2914B, which may include ad content tiles thatmay be customized, contextualized and personalized relative to theuser/asset combination. Likewise, respective gaze vector information2916A/2916B may be provided by the client devices 2912A/2912B to thegaze processing module 2910.

Based on the foregoing, skilled artisans will recognize that embodimentsherein advantageously provide an ad insertion scheme where the displayedad content objects are not only more coherent with the 360-degree videobut are also configured to be placed in a video frame such that theydon't hinder the immersive experience regardless of the projectionmapping scheme used in creating the 3D spatial effect. Further, the adsare embedded within the video and not overlaid, making the ad insertionscheme resilient against ad blocking. Since the ad content tiles arestitched into a muxed frame according to standard video codectechniques, no extra decoder is need for playout by the clients.Additionally, content producers or editors can restrict critical regionswithin a video where such ads cannot be placed and not block any regionsof interest by appropriately setting or configuring insertion policies.On the other hand, ad insertion policies may be particularly definedthat describe which ad(s) to show at what precise time, which can beimplemented strictly with a precision of a few milliseconds since adscan be added or removed during mid-GOP of a video sequence.

One skilled in the art will further recognize that various apparatusesand systems with respect to the foregoing embodiments, as well as theunderlying network infrastructures set forth above may be architected ina virtualized environment according to a network function virtualization(NFV) architecture in additional or alternative embodiments of thepresent patent disclosure. For instance, various physical resources,databases, services, applications and functions executing within anexample streaming network of the present application, including sourcemedia processing infrastructure, media containerization, PE/BIE tileencoding and packaging, etc., set forth hereinabove may be provided asvirtual appliances, machines or functions, wherein the resources andapplications are virtualized into suitable virtual network functions(VNFs) or virtual network elements (VNEs) via a suitable virtualizationlayer. Resources comprising compute resources, memory resources, andnetwork infrastructure resources are virtualized into correspondingvirtual resources wherein virtual compute resources, virtual memoryresources and virtual network resources are collectively operative tosupport a VNF layer, whose overall management and orchestrationfunctionality may be supported by a virtualized infrastructure manager(VIM) in conjunction with a VNF manager and an NFV orchestrator. AnOperation Support System (OSS) and/or Business Support System (BSS)component may typically be provided for handling network-levelfunctionalities such as network management, fault management,configuration management, service management, and subscriber management,etc., which may interface with VNF layer and NFV orchestrationcomponents via suitable interfaces.

Furthermore, at least a portion of an example network architecturedisclosed herein may be virtualized as set forth above and architectedin a cloud-computing environment comprising a shared pool ofconfigurable virtual resources. Various pieces of hardware/softwareassociated with PE/BIE tile encoding and packaging, bandwidth annealingand tile selection, tile muxing and containerization, and the like maybe implemented in a service-oriented architecture, e.g., Software as aService (SaaS), Platform as a Service (PaaS), infrastructure as aService (laaS) etc., with multiple entities providing different featuresof an example embodiment of the present invention, wherein one or morelayers of virtualized environments may be instantiated on commercial offthe shelf (COTS) hardware. Skilled artisans will also appreciate thatsuch a cloud-computing environment may comprise one or more of privateclouds, public clouds, hybrid clouds, community clouds, distributedclouds, multiclouds and interclouds (e.g., “cloud of clouds”), and thelike.

In the above-description of various embodiments of the presentdisclosure, it is to be understood that the terminology used herein isfor the purpose of describing particular embodiments only and is notintended to be limiting of the invention. Unless otherwise defined, allterms (including technical and scientific terms) used herein have thesame meaning as commonly understood by one of ordinary skill in the artto which this invention belongs. It will be further understood thatterms, such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of this specification and the relevant art and may not beinterpreted in an idealized or overly formal sense expressly so definedherein.

At least some example embodiments are described herein with reference toblock diagrams and/or flowchart illustrations of computer-implementedmethods, apparatus (systems and/or devices) and/or computer programproducts. It is understood that a block of the block diagrams and/orflowchart illustrations, and combinations of blocks in the blockdiagrams and/or flowchart illustrations, can be implemented by computerprogram instructions that are performed by one or more computercircuits. Such computer program instructions may be provided to aprocessor circuit of a general purpose computer circuit, special purposecomputer circuit, and/or other programmable data processing circuit toproduce a machine, so that the instructions, which execute via theprocessor of the computer and/or other programmable data processingapparatus, transform and control transistors, values stored in memorylocations, and other hardware components within such circuitry toimplement the functions/acts specified in the block diagrams and/orflowchart block or blocks, and thereby create means (functionality)and/or structure for implementing the functions/acts specified in theblock diagrams and/or flowchart block(s). Additionally, the computerprogram instructions may also be stored in a tangible computer-readablemedium that can direct a computer or other programmable data processingapparatus to function in a particular manner, such that the instructionsstored in the computer-readable medium produce an article of manufactureincluding instructions which implement the functions/acts specified inthe block diagrams and/or flowchart block or blocks.

As pointed out previously, tangible, non-transitory computer-readablemedium may include an electronic, magnetic, optical, electromagnetic, orsemiconductor data storage system, apparatus, or device. More specificexamples of the computer-readable medium would include the following: aportable computer diskette, a random access memory (RAM) circuit, aread-only memory (ROM) circuit, an erasable programmable read-onlymemory (EPROM or Flash memory) circuit, a portable compact discread-only memory (CD-ROM), and a portable digital video disc read-onlymemory (DVD/Blu-ray). The computer program instructions may also beloaded onto or otherwise downloaded to a computer and/or otherprogrammable data processing apparatus to cause a series of operationalsteps to be performed on the computer and/or other programmableapparatus to produce a computer-implemented process. Accordingly,embodiments of the present invention may be embodied in hardware and/orin software (including firmware, resident software, micro-code, etc.)that runs on a processor or controller, which may collectively bereferred to as “circuitry,” “a module” or variants thereof. Further, anexample processing unit may include, by way of illustration, a generalpurpose processor, a special purpose processor, a conventionalprocessor, a digital signal processor (DSP), a plurality ofmicroprocessors, one or more microprocessors in association with a DSPcore, a controller, a microcontroller, Application Specific IntegratedCircuits (ASICs), Field Programmable Gate Array (FPGA) circuits, anyother type of integrated circuit (IC), and/or a state machine. As can beappreciated, an example processor unit may employ distributed processingin certain embodiments.

Further, in at least some additional or alternative implementations, thefunctions/acts described in the blocks may occur out of the order shownin the flowcharts. For example, two blocks shown in succession may infact be executed substantially concurrently or the blocks may sometimesbe executed in the reverse order, depending upon the functionality/actsinvolved. Moreover, the functionality of a given block of the flowchartsand/or block diagrams may be separated into multiple blocks and/or thefunctionality of two or more blocks of the flowcharts and/or blockdiagrams may be at least partially integrated. Furthermore, althoughsome of the diagrams include arrows on communication paths to show aprimary direction of communication, it is to be understood thatcommunication may occur in the opposite direction relative to thedepicted arrows. Finally, other blocks may be added/inserted between theblocks that are illustrated.

It should therefore be clearly understood that the order or sequence ofthe acts, steps, functions, components or blocks illustrated in any ofthe flowcharts depicted in the drawing Figures of the present disclosuremay be modified, altered, replaced, customized or otherwise rearrangedwithin a particular flowchart, including deletion or omission of aparticular act, step, function, component or block. Moreover, the acts,steps, functions, components or blocks illustrated in a particularflowchart may be inter-mixed or otherwise inter-arranged or rearrangedwith the acts, steps, functions, components or blocks illustrated inanother flowchart in order to effectuate additional variations,modifications and configurations with respect to one or more processesfor purposes of practicing the teachings of the present patentdisclosure.

Although various embodiments have been shown and described in detail,the claims are not limited to any particular embodiment or example. Noneof the above Detailed Description should be read as implying that anyparticular component, element, step, act, or function is essential suchthat it must be included in the scope of the claims. Reference to anelement in the singular is not intended to mean “one and only one”unless explicitly so stated, but rather “one or more.” All structuraland functional equivalents to the elements of the above-describedembodiments that are known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the present claims. Accordingly, those skilled in the artwill recognize that the exemplary embodiments described herein can bepracticed with various modifications and alterations within the spiritand scope of the claims appended below.

The invention claimed is:
 1. A method for inserting advertisementcontent in a 360-degree immersive video environment, the methodcomprising: receiving a request from a client device for playing aparticular immersive video asset, wherein each video frame comprises anarray of tiles projected on a 3-dimensional (3D) display environmentviewed by a user operating the client device; selecting a plurality ofvideo tiles of the particular immersive video asset to be assembled as avideo frame for delivery to the client device; obtaining a gaze vectorfrom the client device relative to the particular immersive video asset,the gaze vector defining a field of view (FoV) in the 3D displayenvironment with respect where the user is viewing in reference to aprojected video frame; responsive to the gaze vector, identifying aportion of the video tiles that can be replaced with a corresponding setof advertisement content tiles; replacing the portion of the video tileswith the corresponding set of advertisement content tiles; providing theadvertisement content tiles and the video tiles to a multiplexed streamgenerator for assembling the video frame including the advertisementcontent tiles at select locations; and transmitting the assembled videoframe to the client device.
 2. The method as recited in claim 1, furthercomprising: determining if a tile metadata specification that identifiesadvertisement insertion availability timing information with respect toeach of the plurality of video tiles of the video frame is available; ifso, removing video tiles identified as being unavailable from theportion of the video tiles responsive to the tile metadata specificationto obtain a subset of video tiles as being eligible for replacement;obtaining a plurality of advertisement content tiles corresponding tothe subset of video tiles determined to be eligible for replacement; andproviding the plurality of advertisement content tiles and the subset ofvideo tiles to the multiplexed stream generator for assembling the videoframe including the advertisement content tiles.
 3. The method asrecited in claim 1, wherein the portion of video tiles identified forreplacement with advertisement content tiles are identified furtherresponsive to determining video tiles of the video frame having lowactivity.
 4. The method as recited in claim 3, wherein a subset of thevideo tiles having low activity are determined to be located within thefield of view (FoV) of a display unit associated with the client device.5. The method as recited in claim 1, wherein the plurality of videotiles of the particular immersive video asset are selected from one ormore tile-encoded bitrate representations of the particular video asset,each bitrate representation having a separate video quality.
 6. Themethod as recited in claim 1, wherein the advertisement content tilesare generated from one or more still images of advertisement content. 7.The method as recited in claim 1, wherein the advertisement contenttiles are generated from one or more video sequences of advertisementcontent.
 8. A video server system operative in association with a360-degree immersive video environment, the system comprising: one ormore processors; and persistent memory circuitry having programinstructions stored thereon which, when executed by the one or moreprocessors, perform following acts: receive a request from a clientdevice for playing a particular immersive video asset, wherein eachvideo frame comprises an array of tiles projected on a 3-dimensional(3D) display environment viewed by a user operating the client device;select a plurality of video tiles of the particular immersive videoasset to be assembled as a video frame for delivery to the clientdevice; obtain a gaze vector from the client device relative to theparticular immersive video asset, the gaze vector defining a field ofview (FoV) in the 3D display environment with respect where the user isviewing in reference to a projected video frame; responsive to the gazevector, identify a portion of the video tiles that can be replaced witha corresponding set of advertisement content tiles; replace the portionof the video tiles with the corresponding set of advertisement contenttiles; provide the advertisement content tiles and the video tiles to amultiplexed stream generator for assembling the video frame includingthe advertisement content tiles at select locations; and transmit theassembled video frame to the client device.
 9. The system as recited inclaim 8, wherein the program instructions further comprise instructionsfor performing following acts: determine if a tile metadataspecification that identifies advertisement insertion availabilitytiming information with respect to each of the plurality of video tilesof the video frame is available; if so, remove video tiles identified asbeing unavailable from the portion of the video tiles responsive to thetile metadata specification to obtain a subset of video tiles as beingeligible for replacement; obtain a plurality of advertisement contenttiles corresponding to the subset of video tiles determined to beeligible for replacement; and provide the plurality of advertisementcontent tiles and the subset of video tiles to the multiplexed streamgenerator for assembling the video frame including the advertisementcontent tiles.
 10. The system as recited in claim 8, wherein the portionof video tiles identified for replacement with advertisement contenttiles are identified further responsive to determining video tiles ofthe video frame having low activity.
 11. The system as recited in claim10, wherein a subset of the video tiles having low activity aredetermined to be located within the field of view (FoV) of a displayunit associated with the client device.
 12. The system as recited inclaim 8, wherein the plurality of video tiles of the particularimmersive video asset are selected from one or more tile-encoded bitraterepresentations of the particular video asset, each bitraterepresentation having a separate video quality.
 13. The system asrecited in claim 8, wherein the advertisement content tiles aregenerated from one or more still images of advertisement content. 14.The system as recited in claim 8, wherein the advertisement contenttiles are generated from one or more video sequences of advertisementcontent.
 15. A non-transitory tangible computer readable medium havingprogram instructions stored thereon which effectuate, when executed byone or more processors of a network element, a process for insertingadvertisement content in a 360-degree immersive video environment, thenon-transitory tangible computer readable medium comprising: a codeportion for processing a request from a client device for playing aparticular immersive video asset, wherein each video frame comprises anarray of tiles projected on a 3-dimensional (3D) display environmentviewed by a user operating the client device; a code portion forselecting a plurality of video tiles of the particular immersive videoasset to be assembled as a video frame for delivery to the clientdevice; a code portion for obtaining a gaze vector from the clientdevice relative to the particular immersive video asset, the gaze vectordefining a field of view (FoV) in the 3D display environment withrespect where the user is viewing in reference to a projected videoframe; a code portion, operating responsive to the gaze vector, foridentifying a portion of the video tiles that can be replaced with acorresponding set of advertisement content tiles; a code portion forreplacing the portion of the video tiles with the corresponding set ofadvertisement content tiles; a code portion for providing theadvertisement content tiles and the video tiles to a multiplexed streamgenerator for assembling the video frame including the advertisementcontent tiles at select locations; and a code portion for transmittingthe assembled video frame to the client device.
 16. The non-transitorytangible computer readable medium as recited in claim 15, wherein theprogram instructions further comprise instructions for performing:determining if a tile metadata specification that identifiesadvertisement insertion availability timing information with respect toeach of the plurality of video tiles of the video frame is available; ifso, removing video tiles identified as being unavailable from theportion of the video tiles responsive to the tile metadata specificationto obtain a subset of video tiles as being eligible for replacement;obtaining a plurality of advertisement content tiles corresponding tothe subset of video tiles determined to be eligible for replacement; andproviding the plurality of advertisement content tiles and the subset ofvideo tiles to the multiplexed stream generator for assembling the videoframe including the advertisement content tiles.
 17. The non-transitorytangible computer readable medium as recited in claim 15, wherein theprogram instructions further comprise instructions for selecting theplurality of video tiles of the particular immersive video asset fromone or more tile-encoded bitrate representations of the particular videoasset, each bitrate representation having a separate video quality. 18.The non-transitory tangible computer readable medium as recited in claim15, wherein the portion of video tiles identified for replacement withadvertisement content tiles are identified further responsive todetermining video tiles of the video frame having low activity.
 19. Thenon-transitory tangible computer readable medium as recited in claim 18,wherein a subset of the video tiles having low activity are determinedto be located within the field of view (FoV) of a display unitassociated with the client device.